Courier-IMAP For a general introduction and configuration settings for some popular IMAP clients, go and read imap/README(.html). In this document: * Requirements * Upgrading * Installation * Authentication modules - General notes * Authentication internals * USERDB Authentication module * VCHKPW Authentication module * LDAP Authentication module * DAEMON Authentication module * Using shared folders * CRAM-MD5 Authentication * Sending mail via an IMAP connection Requirements Now is the good time to read the FAQ, before you start. The FAQ is located in the file imap/FAQ(.html?). * C++ compiler - A C++ compiler is required. The server is written in C, but there are some configuration scripts that use C++ code. * NOTE: Courier-IMAP currently does not compile under gcc 3.0 * make - Th e GN U ma ke is re commended. So laris's make is to be avoided. xBSD already has a gmake port, install it and use it (use gmake everywhere this document refers to make). * GDBM/DB - either the GDBM or the Berkeley DB library is required. * OpenLDAP/MySQL/PostgreSQL/OpenSSL - The IMAP server can optionally use a database back end for authentication. The database back end can be either an LDAP directory, a MySQL database, or a PostgreSQL database. The IMAP server can also implement IMAP over SSL (STARTTLS) as well. Generally, to enable the optional modules it is only necessary to install OpenLDAP, MySQL, PostgreSQLor OpenSSL. The configuration script checks for presence of these libraries, and compiles the appropriate files. Note: these packages MUST BE installed in directories that are searched by your C compiler by default. Some installation scripts default to installing the development libraries and include files in custom directories. In that case it will be necessary to set some environment variables, before running the configure script, to specify additional options to the compiler that add the custom directories to the compiler's search path. See the FAQ for more information. You also need to make sure that all the supporting DEVELOPMENT files are installed. Most LDAP/MySQL/PostgreSQL packages come in two parts: the runtime support, and development support. You may have just the runtime support installed, you will need to make sure that development support files are also installed. UPGRADING Upgrading from Courier-IMAP 1.3.0, and later versions, is a straightforward process. Follow the instructions in the INSTALLATION section, below, to install the new version. The "make install-configure" command automatically preserves the existing system configuration. However, note that new versions of Courier-IMAP will often introduce additional configuration options. After make install-configure a cursory inspection of configuration files in /usr/lib/courier-imap/etc (the default location of the configuration directory) is recommended, in order to identify any new configuration settings that might need adjustment. Upgrading from Courier-IMAP 1.3.8.2 and earlier The default configuration options have slightly changed. The default configuration script will now always build the authdaemon module, and build all real authentication modules inside authdaemond. This is true even with the authvchkpw module. Upgrading from Courier-IMAP 1.2.3 and earlier Courier-IMAP 1.3.0 introduced a new configuration file format that allows configuration files to be automatically upgraded. Additionally, several existing configuration files have been renamed in order for their names to be consistent with the Courier build: Courier-IMAP < 1.3 Courier-IMAP 1.3.0 -------- --------- imapd.config imapd imapd-ssl.config imapd-ssl pop3d.config pop3d pop3d-ssl.config pop3d-ssl The NEWS file has a detailed explanation of how configuration files are now installed. Basically, make install now installs configfilename.dist, and make install-configure copies configfilename.dist to configfilename, becoming the actual configuration file. If there is an existing configfilename, the old settings in configfilename which are still valid will be kept in the new configfilename. This only works as long as both the old and the new configuration files are in the new format, so this will actually take effect with your next upgrade Courier-IMAP. If the previous installed version of Courier-IMAP did not use the new format for configuration files (1.2.3 and earlier), the old configuration file is backed up to configfilename.bak. The recommended procedure for upgrading from versions 1.2.3 and earlier is as follows: The recommended upgrade procedure is as follows: * Back up /usr/lib/courier-imap/etc * Follow the installation procedures, below * After installing, manually edit all configuration files. Restore, by hand, any custom configuration settings. All configuration files are kept in the configuration directory. Nothing else in /usr/lib/courier-imap is configurable. Do not simply overwrite 1.3.0 configuration files with configuration files from the previous version. It's tempting, but don't do it. It may work, but you will lose the automatic upgrade capability for future releases. Upgrading from Courier-IMAP 1.1 or earlier Note that Courier-IMAP 1.2 includes a compatible POP3 server, and the installation script will also install a POP3 server on your system. Even though it is installed, you are not required to use it, but you still need to be aware of its existence. If you install the RPM build of Courier-IMAP, you're going to get the POP3 server started at system boot. If you do not need POP3 services, edit both the pop3d.config and pop3d-ssl.config configuration files, and set POP3DSTART and POP3DSSLSTART to NO Upgrading from Courier-IMAP 1.0 or earlier If the server is running, manually stop the server before installing the new version. INSTALLATION To compile and install the Courier-IMAP server (this is the short version, a longer version follows): $ ./configure [ options, see below ] $ make $ make check # Note - the --enable-workarounds-for-imap-client-bugs # option to configure will result in make check FAILING. $ su root # make install # Or, make install-strip, to strip the executables. # make install-configure # Install configuration files. # Start the authdaemond process NOTE You MUST run the configure script as normal user, not root. Did you extract the tarball as root? It won't work. Remove the extracted source code. Log in as a normal user. Extract the source code as a normal user, then run configure. You will do everything as a normal user, except for the final step of installing the compiled software. _________________________________________________________________ As mentioned in "Requirements", above, if you are using xBSD, you must use gmake instead of make. _________________________________________________________________ NOTE: The configure script may run as much as 5-10 minutes on slow machines. It may appear that configure is stuck in a loop, but that's an illusion. Courier-IMAP is built from a collection of modular components, each with its own configuration script. The configuration scripts share a lot of common code, leading to an initial impression that the same configuration script is being repeatedly run. See below for a description of the options to the configure script. WARNING: set your umask to 022 before running make install or make install-strip. You should try make install-strip first. Use make install if make install-strip fails. The configure script accepts certain options, but the defaults should be fine most of the time. make install puts everything in /usr/lib/courier-imap. If the directory /etc/pam.d exists, make install creates /etc/pam.d/imap and /etc/pam.d/pop3, overwriting any existing files. If you have some other IMAP server installed, this means that you will want to save your existing configuration in /etc/pam.d/{imap|pop3}. "make check" performs some internal sanity checks. If make check fails, something is wrong, and Courier-IMAP may not work for you reliably. Certain options are documented to cause make check to fail, due to different IMAP protocol behavior. If you need to use those options, first compile Courier-IMAP without them, run make check, and if all goes well extract the source code again in a different directory, then build it for the second time using your options. After installation, you will need to review the files in /usr/lib/courier-imap/etc and make any changes you deem necessary, including: * If you do not want to create and use virtual mailboxes, you should remove authuserdb from AUTHMODULES. If AUTHMODULES contains "authdaemon", you will have another configuration file, authdaemonrc. Remove authuserdb from authdaemonrc instead. * The configuration script automatically selects whatever authentication modules can be used on your system, but you may not necessarily want to use them. For example, if your system has OpenLDAP libraries installed, the authldap module gets compiled and installed, even though you might use LDAP for some other purposes, not necessarily authentication. If that's the case, remove authldap from the AUTHMODULES entry in the imapd configuration file, or from authdaemonrc, whatever the case might be. * If you're using PAM authentication (authpam gets compiled and installed), you will have to tell your PAM library how to authenticate the "imap" service and the and "pop3" service (if you intend to use the bundled POP3 server too). What you need to tell your PAM library is something that you will have to figure out by yourself, because it depends on the version of your PAM library, and your operating system. If the directory /etc/pam.d exists, the installation script will automatically install /etc/pam.d/imap and /etc/pam.d/pop3, but that's just for starters. You will still have to inspect its contents and adjust the full pathname to the PAM modules, if necessary. Some versions of the PAM library, do not use the /etc/pam.d directory. Instead they use a single configuration file /etc/pam.conf. Here's an example of what needs to be added to /etc/pam.conf on FreeBSD 4.0. NOTE: other platforms may need something similar: imap auth required pam_unix.so try_first_pass imap account required pam_unix.so imap session required pam_permit.so pop3 auth required pam_unix.so try_first_pass pop3 account required pam_unix.so pop3 session required pam_permit.so Your PAM library may use pam_pwdb.so instead of pam_unix.so; consult the documentation for your PAM library for more information. configure should automatically detect if you use vpopmail, and compile and install the authvchkpw authentication module. After running make install or make install-strip you will then have to modify your system's startup scripts to run Courier-IMAP when your system boots. Use the following command to start the Courier-IMAP server: $ /usr/lib/courier-imap/libexec/imapd.rc start This assumes that Courier-IMAP is installed in /usr/lib/courier-imap. Use the following command to stop Courier-IMAP: $ /usr/lib/courier-imap/libexec/imapd.rc stop You will have to add these commands to your system startup/shutdown scripts. IMAP over SSL To add SSL support you have to install OpenSSL before installing Courier-IMAP. Download OpenSSL from http://www.openssl.org/. Follow the instruction in OpenSSL package to install it and configure it. SSL support in Courier-IMAP has been tested with OpenSSL 0.9.5a. The /usr/lib/courier-imap/lib/imapd-ssl configuration file sets some additional options for SSL support, which you may need to adjust. Consult that configuration file for additional information. Then, you also have to run the /usr/lib/courier-imap/libexec/imapd-ssl.rc script from your system startup and shutdown scripts, just like the /usr/lib/courier-imap/libexec/imapd.rc script. You may accept both SSL and non-SSL connections by running both scripts. Note that SSL requires a valid, signed, X.509 certificate to be installed where Courier-IMAP expects to find it. The default location for the X.509 certificate, in PEM format, is /usr/lib/courier-imap/share/imapd.pem. The X.509 certificate must be signed by a certificate authority that is known to the IMAP client. You can generate your own self-signed certificate by running the script /usr/lib/courier-imap/share/mkimapdcert which will work too, except that IMAP clients using SSL will display a warning message the first time they connect to the server. To get rid of the warning message you'll have to pay for a signed X.509 certificate. The gory details of setting up SSL is beyond the scope of this document, and you should consult the OpenSSL documentation for more information. The mkimapdcert script will not overwrite an existing imapd.pem certificate, in order to allow precompiled packages to simply call mkimapdcert after installation, without worry. The bundled POP3 server The POP3 server included with Courier-IMAP provides POP3 access to INBOX, and that's about it. Enabling the POP3 server is very similar to enabling the IMAP server, with the following differences: The configuration files are /usr/lib/courier-imap/etc/pop3dand /usr/lib/courier-imap/etc/pop3d-ssl. The startup/shutdown scripts are /usr/lib/courier-imap/libexec/pop3d.rcand /usr/lib/courier-imap/libexec/pop3d-ssl.rc. The SSL certificate is /usr/lib/courier-imap/share/pop3d.pem, and the /usr/lib/courier-imap/share/mkpop3dcert script can be used to create a self-signed SSL certificate for testing purposes. System-V style startup If your system uses System-V style startup scripts, take a look at courier-imap.sysvinit - this is a sample /etc/init.d script. courier-imap.sysvinit is created by configure. In most cases it can be merely copied to /etc/init.d and /etc/rc?.d directories (with the execute permission bit turned on). The sample startup script will check if IMAP or POP3 over SSL is enabled. The sample startup script automatically creates dummy SSL certificates the first time it is executed. Options to configure: * --prefix=pathname - install here, instead of /usr/lib/courier-imap * --without-ipv6 - do not compile IPv6 support. The configure automatically checks if IPv6 support is available, and enables it automatically. This option suppresses IPv6 support, even if it's available. IPv6 support means that Courier-IMAP will create an IPv6 socket and accept IPv6 connections. --without-ipv6 should be used if your system does not fully support IPv6, or if its implementation is buggy. Most Linux distributions now ship with IPv6 support in glibc, but without compiling the kernel for IPv6 support. This results in modprobe regularly complaining in /var/log/messages about the fact that it can't load the IPv6 module. Use --without-ipv6 to turn off IPv6 support, if that bothers you. * --enable-unicode - include the ability to search and sort messages in character sets other than the default ISO-8859-1/US-ASCII. All character set tables supported by Courier-IMAP will be included. See below for more details. * --enable-unicode=charset,charset,... - include ability to search and sort messages, but only for these character sets. See below for more details. * --without-module - explicitly specify that the authentication module named "module" should not be installed. See below for more details. Example: --without-authdaemon. * --bindir=pathname , --mandir=pathname - override default names of subdirectories under prefix. See below for more information. * --with-db=db - Use the DB library instead of the GDBM library You must have either the GDBM or the DB library installed. If both are present, GDBM is selected unless you use this option. The GDBM/DB library is used by Courier for certain functions. * --with-piddir=dir - use dir/imapd.pid to store couriertcpd's process ID. * --with-userdb=file - use file instead of /etc/userdb (also means that userdb.dat and userdbshadow.dat are appropriately renamed). * --enable-workarounds-for-imap-client-bugs - there are a number of various bugs in certain IMAP clients. The current list of broken IMAP clients consists of Netscape Messenger and Sun's StarOffice. This option enables some workarounds for some bugs in these clients, however, note that this may break compatibility with software that correctly implements IMAP4rev1. Additionally, "make check" will fail when this option is used. See imap/BUGS.(html|txt) for more information. NOTE - if this option is used, make check WILL FAIL. You should first configure Courier-IMAP without this option, run make check, then reconfigure Courier-IMAP with this option. * --with-trashquota - include deleted messages, and the Trash folder, in the estimated quota usage for maildirs. Quotas are optional, see the file maildir/README.maildirquota.html for more information. The default configuration does not count messages marked as deleted (but not yet expunged) and the contents of the Trash folder (which are automatically purged by the server) against the quota usage. Foreign character set sorting/searching The Courier-IMAP server can search and sort messages using other than the default us-ascii/iso-8859-1 character set. You can find the list of available character sets in the file unicode/charsetlist.txt. The default is to include only the ISO-8859-1/US-ASCII character set. Use the --enable-unicode option to include all available character sets. It is also possible to include translation tables only for selected character sets. Example: --enable-unicode=iso-8859-1,utf-8,iso-8859-10 Technically, IMAP servers must support the UTF-8 character set, however few IMAP clients (I've yet to see one, actually) care about UTF-8, so the UTF-8 character set is optional in Courier-IMAP. The only required character set - which is always included, explicitly or implicitly - is ISO-8859-1/US-ASCII. Note that character set translation tables need substantial memory. This should not be a problem in most cases. Most compilers will place the read-only character set tables into a shared text segment, that's shared by all running servers. --enable-unicode should not really be much of a burden for most modern operating systems. Attentive individuals will observe that all character set tables are compiled even without the --enable-unicode option. That is normal -- only the explicitly selected character set tables will actually make it into the final executable. Installation directories Unless the options --prefix, --bindir, or --mandir are used, everything will be installed in the directory /usr/lib/courier-imap. Use the --prefix option to specify a different directory. This directory will have the following subdirectories: * etc - configuration files * bin - binaries * sbin - superuser binaries * libexec - additional binaries * man - manual pages * share - scripts and data files * var - temporary files used by the authdaemond, daemon process (if the authdaemon authentication module is selected). Having everything installed underneath one directory allows its contents to be easily backed up, before a newer version of courier-imap is installed. Reverting to a previous version is as simple as restoring from backup. Because some binaries in bin and sbin may be executed from the command line, it will be necessary to change your systemwide global startup script to add this directory to the default PATH. Additionally, it will also be necessary to modify the configuration of the man(1) command so that it can find Courier-IMAP's manual pages in this directory: PATH="/usr/lib/courier-imap/bin:$PATH" if test -w /etc then PATH="/usr/lib/courier-imap/sbin:$PATH" fi export PATH MANPATH="/usr/lib/courier-imap/man:$MANPATH" export MANPATH As an alternative, you may use the --bindir and --mandir options in order to install binaries to /usr/local/bin and the manual pages to /usr/local/man, which should already be searched by default: ./configure --bindir=/usr/local/bin --mandir=/usr/local/man Other familiar configure options, such as --sysconfdir and --datadir work too, for those who know how to properly use them. AUTHENTICATION MODULES - GENERAL NOTES An authentication module does a few things besides checking if a userid and password are valid. It's job also includes specifying the location of the primary maildir, and its system user and group id. There are several authentication modules available. Each authentication module implements a different way of authenticating logins, and not all authentication modules can be used by everyone. Some authentication modules can be used only on systems that have certain libraries or software installed separately. The configure script checks if the required libraries and software are available for each authentication module. If the required libraries and support files are available, the configure script includes the corresponding authentication module. The option --without-module instructs configure not to compile an authentication module, even if it could. Multiple --without options are, of course, allowed (each one specifying a different authentication module). * authpwd - this module looks up userids and passwords in your /etc/passwd file, or the equivalent NIS map (as supported by your system's getpw library). * authshadow - this module is like authpwd, except that it should be used on systems that use shadow password files, /etc/shadow. * authpam - this module should be used on systems that have the PAM library. With this module, Courier-IMAP will use whatever PAM modules you specify for authenticating the "imap" PAM service. Essentially, authpam allows any PAM module to be used for authenticating logins. NOTE: in addition to including this module, you will have to take additional, site-specific, steps in order to configure your PAM library for the "imap" PAM service. The specific details regarding your PAM configuration differs from system to system, and you should consult your own documentation. It might be tempting to throw in a towel and use authshadow or authpwd if you cannot figure out how to install PAM support, however that is not advisable. It is highly recommended to use authpam wherever the PAM library is available. Additionally: PAM is used only for password validation. The home directory and the user and group IDs for the account are still taken from the system password file. * authuserdb - this module uses GDBM or DB database files, usually /etc/userdb.dat and /etc/userdbshadow.dat to look up userids and passwords. These files are GDBM or DB databases that are loosely equivalent in function to /etc/passwd and /etc/shadow. These databases are maintained indirectly by several Perl scripts - included with Courier-IMAP - which build these database files from a plain text file, usually called /etc/userdb. This file can be modified by any text editor, or it can be managed by some useful Perl scripts which are included. /etc/userdb may also be a subdirectory that has multiple text files in the same format, which are simply concatenated. userdb allows creation of virtual mail accounts that do not have a corresponding login account -- virtual mail accounts that can share the same, reserved, system userid. /etc/userdb can also be used to completely supersede /etc/passwd. With many accounts it can be quite a drain to have to continuously linearly scan /etc/passwd in order to look up an account. Instead, a fast database lookup can retrieve the same information from the database file. Read the included manual pages, starting with userdb(8) for more information. * authcram - this module is similar to authuserdb (it uses the same databases), but implements CRAM-MD5 authentication. See below for more information. * authvchkpw - this is another virtual mail database lookup module, except that it uses the vpopmail vpasswd files. This module is provided for a quick way to use your existing vpopmail vpasswd files. Where possible, you should convert over to /etc/userdb. The included script vchkpw2userdb(8) might be of some help in doing so. * authldap - authenticates against an LDAP server. This is a new module included with Courier-IMAP. See below for more information. * authmysql - native MySQL authentication module Read authlib/README.authmysql for information on how to set up this module. * authpgsql - native PostgreSQL authentication module PostgreSQL configuration is nearly identical to MySQL information, see authlib/README.authpostgres.html for more information. * authdaemon - background daemon authentication proxy. See below for more information. * authcustom - this is a dummy authentication module that dose not authenticate anything. It is a placeholder that can be used to implement any site-specific authentication code, written in C. To implement some site-specific authentication, inspect the contents of the authlib/preauthcustom.c file for additional instructions. It is possible to include more than one authentication module. For example, if you select both authuserdb and authpam, each login will first be authenticated against /etc/userdb. If Courier-IMAP cannot find the account in /etc/userdb, it will then attempt to authenticate using the PAM library. configure uses the following logic to determine which authentication modules will be included by default: * authuserdb/authcram - these modules are always included by default * authpam - configure attempts to detect if the PAM library is installed, or not. --without-authpam can be used to avoid installing authpam on systems that do have a PAM library installed. Hopefully, you will have a good reason to do something this silly. * authldap - configure checks if OpenLDAP is installed. If OpenLDAP development libraries are available, authldap will be compiled and installed. * authpwd , authshadow - whether or not these modules are installed by default depends upon what happened with authpam and authldap. If PAM or LDAP support is installed, via authpam or authldap, these two modules are usually not necessary, because the PAM library, or the LDAP server, provides this functionality. If PAM support is unavailable, these modules will be installed by default. * authvchkpw - this module is compiled by default only if the vpopmail account is defined. * authmysql - this module is compiled if MySQL client libraries are available. * authpgsql - this module is compiled if PostgreSQL client libraries are available. * authdaemon - this module is always compiled by default. See below for more information. Confirming selected authentication options You can find out what authentication modules were actually used, but you must first run make successfully. Running make compiles the authinfo program in the authlib subdirectory. This program tells you what authentication modules were compiled. USERDB AUTHENTICATION MODULE userdb is a way to implement many virtual mailboxes - many mailboxes that do not have to have a separate system userid allocated for each one, and there is no system login associated with each mailbox. userdb uses a database for mapping virtual addresses to physical maildirs. It should be scalable to thousands of mailboxes. It can also be used to replace linear searches of /etc/passwd with a database lookup, see pw2userdb(8). Note - you still MUST use some valid system userid and groupid that is shared by all virtual mailboxes. Instead of allocating a single userid and groupid per each mailbox, the same userid and groupid is used for all of them. This is a rough overview of using userdb. For additional information, read makeuserdb(8), and userdb(8). All the scripts will be installed in /usr/lib/courier-imap, so look for them there. Courier-IMAP can use the userdb database simply by the virtue of installing the authuserdbauthentication module, which happens by default. The tricky part is creating the database. Hopefully, it's only tricky once, and the second time it won't be so tricky any more. The userdb configuration is extremely flexible, and there are many ways of actually setting up the database. The best way to describe how userdb works is to try to create one virtual mail account. As mentioned before, virtual mailboxes still need one system account to be used for uid/gid purposes. Let's call this system account "vmail". Simple userdb setup. This approach should be used if you do not have many virtual mailboxes. It's very simple, but quickly becomes cumbersome if you administer many virtual mailboxes. Create an empty /etc/userdb. # cp /dev/null /etc/userdb # chmod 700 /etc/userdb /etc/userdb must have 700 permissions. Now, run the script pw2userdb. This script converts the contents of your /etc/passwd to the /etc/userdb format (including the contents of /etc/shadow, this is why permissions on /etc/userdb must be 700). This script is usually used where you want to convert a very large /etc/passwd to /etc/userdb. userdb applications can now use a fast userdb database instead of a linear scan of /etc/passwd in order to look up system accounts. However, you probably don't want to do use this feature right now, so what you simply want to do is take the output of pw2userdb, and find the entry for the vmail account that you created earlier. Look for a line that starts with 'vmail' followed by tab, followed by familiar fields from /etc/passwd. Save the output of pw2userdb in a temporary file, edit it, and remove everything except the line containing vmail, and the very next line, which is a special entry that maps vmail's userid back to the vmail record. Here's what you might find in the output of pw2userdb: vmail uid=1012|gid=1012|home=/home/vmail|systempw=* 1012= vmail The actual numerical values and the home directory location may vary. Save these two lines as /etc/userdb, and set the permissions on /etc/userdb to 700: $ chmod 700 /etc/userdb Now, with that out of the way, let's really create a virtual account. In this example we'll create a virtual mailbox for 'john@example.com'. # su vmail $ cd $HOME $ maildirmake Maildir-john-example $ exit # You may need to specify a full path to your maildirmake program. The end result is that you created $HOME/Maildir-john-example in vmail's account. The next step is to configure your mail server to deliver mail for john@example.com directly into the maildir ~vmail/Maildir-john-example. How that's done depends on the mail server that you use. Now, let's connect the dots here, and create an entry in /etc/userdb for john@example.com: # userdb "john@example.com" set home=/home/vmail \ mail=/home/vmail/Maildir-john-example \ uid=UUU gid=GGG This command runs a Perl script named userdb , which is installed, by default in /usr/lib/courier-imap/sbin. Replace UUU and GGG with the userid and groupid of the vmail account. If you now look in /etc/userdb, you will see that a new record for john@example.com has been appended to the end of the file. We're not finished yet. We need to set the IMAP password for this mailbox: # userdbpw | userdb "john@example.com" set imappw If you are running Red Hat Linux 6.0, or higher, you can specify the -md5 option to userdbpw, in order to use an MD5 password hash, instead of crypt. Specify "systempw" instead of "imappw" if you would like to use the same password for the POP3 server too. The imappw field is only checked by the IMAP server. If not defined, systempw is used instead. The field pop3pw will be checked by the POP3 server that's bundled with Courier-IMAP. If it is not defined the POP3 server will check systempw too Finally, compile the database: # makeuserdb This command creates the actual database, /etc/userdb.dat and /etc/userdbshadow.dat from the plain text file /etc/userdb. Courier-IMAP will now start accepting logins to this mailbox. Adding and removing mailboxes can be done while Courier-IMAP is running. Courier-IMAP reads /etc/userdb.dat and /etc/userdbshadow.dat only. The plain text source, /etc/userdb is not read by Courier-IMAP itself. Changes take effect only when makeuserdb runs. Large virtual domain farm. The previous approach uses a single flat file, /etc/userdb. This might be a bit cumbersome if you have thousands of virtual mailboxes in many domains. Here's an alternative approach that can scale to thousands of domains and mailboxes. Instead of creating a /etc/userdb file, create a subdirectory: # mkdir /etc/userdb # chmod 700 /etc/userdb Now, create /etc/userdb/default, containing pw2userdb's output for the vmail account, as previously described. This time, you probably want to create all mailboxes for the same domain in a separate subdirectory: # su vmail $ cd $HOME $ mkdir -p domains/example-com $ maildirmake domains/example-com/john $ exit The idea is that all the maildirs for @example.com will be stored in ~vmail/domains/example-com. All maildirs for domain.org will be stored in ~vmail/domains/domain.org. The actual layout and naming conventions are entirely up to you to define. Now, configure your mail server to deliver mail for john@example.com into this maildir. Here's how configure /etc/userdb. $ userdb "example-com/john@example.com" set home=/home/vmail \ mail=/home/vmail/domains/example-com/john \ uid=UUU gid=GGG This creates the file /etc/userdb/example-com (the first parameter to the userdb command), and appends a record named "john@example.com". You will store all userdb entries for @example.com in the file /etc/userdb/example-com. All entries for @domain.org will be maintained in /etc/userdb/domain-org, and so on. $ userdbpw | userdb "example-com/john@example.com" set imappw This sets the IMAP access password for this account. Finally: $ makeuserdb VCHKPW AUTHENTICATION MODULE This authentication module is provided for legacy support. New installs should use the authuserdb module. It is possible to convert vpopmail/vchkpw single userid authentication passwd files to /etc/userdb using the vchkpw2userdb script. See vchkpw2userdb(8) for more information. LDAP AUTHENTICATION MODULE This module attempts to authenticate against an LDAP server. This option installs a sample configuration file, which is /usr/lib/courier-imap/etc/authldaprc by default. You will need to edit this file in order to configure LDAP authentication. This configuration file defines the location of your LDAP server, as well as the names of attributes used to perform LDAP authentication. See the comments in the sample configuration file, and the authldap(8) manual page, for more information. DAEMON AUTHENTICATION MODULE Selecting the authdaemon module (it is selected by default) will compile and install a separate process, called "authdaemond". The "authdaemond" process is started and stopped by the imapd.rc, imapd-ssl.rc, pop3d.rc and pop3d-ssl.rc. ATTENTION: all four scripts stop authdaemond. Typically all the scripts are called together, at system startup and shutdown. If you need to stop just ONE service, find the pid and kill it manually. Otherwise authdaemond stops and nobody can log in anymore. The authdaemon module (and the authdaemond process that goes with it) is very useful when a database is used as an authentication back-end (like MySQL, PostgreSQL, or OpenLDAP). The authdaemon module offers an alternative to compiling all the authentication code as standalone modules. Enabling authdaemon in addition to any other modules will result in authdaemon being built as the only "official" authentication module. All other modules are compiled into a separate process, "authdaemond". Certain authentication modules -- such as authldap, authpgsql and authmysql -- connect to an external database in order to validate an authentication request. The database connection is created and destroyed for every login request, and with a large number of connections and authentications it is better to have a single daemon process running in a background, with a semi-permanent connection to the database, handling authentication requests. That's exactly what authdaemond does. The authdaemon authentication module takes an authentication request, and forwards it to the permanently running authdaemond process, waits for the answer, and returns the result to the application. Courier-IMAP, by the virtue of its modular design, "sees" only the authdaemon authentication module. Behind the scenes, authdaemon takes every authentication request and passes it along to the authdaemond for processing, where all the real authentication happens. The /usr/lib/courier-imap/etc/authdaemonrc configuration file sets several parameters for the authdaemond process. See the comments in this file for more information. Currently, authdaemonrc sets two parameters: number of daemon processes, and which available authentication modules are used. Although authdaemond might be built with several authentication modules, not all of them must be used. This allows for a single authdaemond binary to be made that gets installed on multiple systems with different authentication needs. The default module list specified in authdaemonrc is a list of all the available authentication modules. All available authentication modules are compiled by default. Although it is possible to disable unwanted authentication modules via the configure script, it is better to disable them at runtime. The list of all active authentication modules is read from the authdaemonrc configuration file. Removing an authentication module from this configuration file disables it. The number of authdaemond processes is also set in this configuration file. The more processes that are started, the more authentication requests can be handled. If authdaemon does not receive an answer within some amount of time, it will assume an authentication failure, and abort. Try increasing the number of processes if you start seeing random authentication failures. However, that should only be used as a stop-gap measure. If the default number of authdaemond processes proves to be insufficient, it is far more likely that more resources are needed for the server (more RAM, a faster disk, or a faster CPU) in the humble opinion of the author. Increasing the number of processes should only be used as a stop-gap measure, until a more thorough analysis of the system performance. After making any changes to authdaemonrc, run the following command for these changes to take effect: /usr/lib/courier-imap/libexec/authlib/authdaemond restart Alternative authdaemond modules /usr/lib/courier-imap/libexec/authlib/authdaemond is actually a script. Depending on your system configuration, there may be one or more different authdaemond binaries installed, and here's why. authdaemond.plain will include all available authentication modules except for certain "heavy" authentication modules. The current list of "heavy" authentication modules is authldap, authpgsql, and authmysql. If support for a "heavy" authentication module is selected, there will be an additional binary installed, such as authdaemond.mysql, authdaemond.pgsql or authdaemond.ldap. The /usr/lib/courier-imap/libexec/authlib/authdaemond script checks if any "heavy" authentication daemon is installed, and, if so, runs that. Otherwise, the default authdaemond.plain binary goes in. This allows an easy way to create binary Courier-IMAP distributions with and without LDAP, MySQL, or PostgreSQL support. The distributor would simply build Courier-IMAP on a machine that contains both LDAP/MySQL/PostgreSQL development libraries, then take everything but authdaemond.mysql, authdaemond.pgsql and authdaemond.ldap and roll it into the base Courier-IMAP package. authdaemond.mysql, authdaemond.pgsql, and authdaemond.ldap are rolled into separate sub-packages. Loading a base package installs basic system authentication services. Adding LDAP, MySQL, or PostgreSQL support is as simple as loading the corresponding sub-package. USING SHARED FOLDERS Courier-IMAP supports shared folders. See the file README.sharedfolders.html for information on how to set up shared folders. CRAM-MD5 AUTHENTICATION CRAM-MD5 authentication allows IMAP clients to authenticate themselves without sending the password in clear-text over the network. Courier-IMAP now supports CRAM-MD5 by default, but is not enabled for reasons explained below. CRAM-MD5 support is implemented by the authcram module, with one exception - authldap, authpgsql, and authmysql support CRAM-MD5 authentication if the LDAP or the MySQL/PostgreSQL server stores clear-text passwords, and not crypt-ed passwords. To use CRAM-MD5 it is necessary to use an IMAP client that support CRAM-MD5 authentication, of course. That's the easy part. The problem is that it is not possible to use the system password when logging in using CRAM-MD5. That's because CRAM-MD5 requires the knowledge of the actual password, in the clear, in order to calculate authentication tokens (even though that the password itself is not sent in the clear over the network). So, implementation of CRAM-MD5 is an advanced task that should be attempted only when you are comfortable with, and fully understand how Courier-IMAP works in general. Here's an overview of this procedure: * Install and implement /etc/userdb, because CRAM-MD5 authentication uses the /etc/userdb database (but see below for LDAP-specific notes). * Figure out which accounts are going to use CRAM-MD5 authentication. People who do not use an IMAP client that supports CRAM-MD5 can continue and log in with the existing system password. But everyone who runs a client that supports CRAM-MD5 authentication will need a new password. Also, it will be necessary to set up CRAM-MD5 passwords for everyone at the same time. As soon as CRAM-MD5 authentication is enabled, all CRAM-MD5 enabled clients will attempt to use it. If no password is available, Courier-IMAP has no choice but to reject the authentication attempt. Once that happens, the client will correctly interpret it as an authentication failure (and it is), and the client will not even try to authenticate using the system password. Use the following command to assign a CRAM-MD5 password: userdbpw -hmac-md5 | userdb userdb set hmac-md5pw Then run the makeuserdb command, as always. * NOTE: CRAM-MD5 authentication is also be supported by authldap, authpgsql and authmysql, as long as clear-text passwords are used. See below for more information. Therefore, if you use LDAP, PostgreSQL, or MySQL, and you store clear-text passwords, you should all set and ready to go, and you do not need to install /etc/userdb, as described in this section. Enabling CRAM-MD5 authentication Because of these unfortunate complexities, CRAM-MD5 authentication is disabled after installation. When you're ready to use CRAM-MD5, edit the imapd configuration file and add the "AUTH=CRAM-MD5" keyword to the IMAP_CAPABILITY environment variable, then restart Courier-IMAP. There are instructions in the imapd configuration file to that effect. If you do not intend to ever use CRAM-MD5 authentication, you can either specify --without-authcram option to the configure script, or simply edit imapd and remove authcram from the AUTHMODULES setting. SENDING MAIL VIA AN IMAP CONNECTION This server allows using the IMAP connection to send E-mail. Normally, the IMAP protocol provides only access to mail in an existing mail account, and mail clients must use SMTP in order to send mail. The Courier-IMAP server has an optional setting to enable mail to be send via an IMAP connection in a manner that should work with all existing IMAP mail clients. This can be useful when an account is logged in from a shared access pool which normally blocks most access to the SMTP port. This is implemented by enabling a setting in the imapd configuration file that designates a folder as a special "Outbox" folder. The default setting is a folder called "Outbox" (IMAP path INBOX.Outbox), but the name can be changed to anything. This folder, for the most part, is no different than any other folder. If a folder by that name doesn't exist, it needs to be created, just like any other IMAP folder. It looks and acts like any other folder, except that each message added to the folder, via IMAP's APPEND or COPY command, will also be mailed out by the Courier-IMAP server to the addresses listed in the To:, Cc:, and Bcc: headers. It should be possible to use this to send mail from any IMAP client by: 1. Composing a draft message, telling the IMAP client to save the draft message in its drafts folder on the IMAP server. 2. Opening the drafts folder, and moving or copying the message to the Outbox folder. 3. The act of copying the message into the Outbox folder will send the mail. There won't be any explicit notification to the fact that the message was sent, so it's a good idea to include your own E-mail address on the Cc: list. NOTE: it is tempting to configure the IMAP mail client to use Outbox as its default folder for saving drafts. Resist the temptation. If you forget, you'll save a partially completed draft, which will be then obediently mailed out. NOTE: the message, in addition to being sent, will be saved in the folder in the normal fashion. After saving the message, reopen the Outbox folder and delete the sent message, or move it someplace else. NOTE: when enabled, the Courier-IMAP server will advertize a private XCOURIEROUTBOX IMAP capability. It is theoretically possible to code an IMAP mail client that reads this capability and automatically configures itself accordingly -- when this IMAP capability is present -- to send E-mail in the normal way but using the IMAP connection. At this time, I'm not aware of any actual mail clients that know how to do this. NOTE: many mail clients save some additional internal information in headers of draft messages. The internal information is normally removed before the mail client sends the message. Make sure that none of this extra information is something that should not be mailed out.