SquirrelMail configuration is file based.

If you've installed SquirrelMail directly from source you'll find the configuration file in config/config.php, but if you're using a SquirrelMail package from your OS distribution the actual configuration file may be located somewhere else (such as /etc/) - usually with a symbolic link from config/config.php. Read the documentationthat came with the distribution package to find out more about OS distribution specific details.

The rest of these instuctions assumes that you've installed SquirrelMail from source. There are three ways to change the SquirrelMail configuration file: using the configuration tool, using the Administrator plugin, or editing the configuration file manually. The first of these ways is the one recommended by the SquirrelMail Project.

Please note that if there are users logged in when the configuration is changed, those users might not be affected by the changes until after they have logged out.

This is a side effect of the caching of data for logged in users. The configuration tool included in the SquirrelMail distribution is a Perl script,located at config/conf.pl, which helps when creating or editing the configuration file. The first thing to do when configuring from scratch is to choose an IMAP server using "Set pre-defined settings for specific IMAP servers". This will change SquirrelMail configuration to match a default installation of the IMAP server of your choice.

The next step is to go through all the menu selections and set the configuration options to the values most suitable for your installation. Each configuration option is described in the tool to help you make the right choices. Even if you don't have Perl accessible at the computer where SquirrelMail is insalled, you can use config/conf.pl if you have access to a computer with Perl installed. Just copy config/conf.pl to the computer with Perl, use it to create a configuration file, and then upload the configuration file to config/config.php in your SquirrelMail installation.

Note that some OS distributions have their own tools to configure SquirrelMail, which you might use instead (Debian, Ubuntu, and other Debian derived distributions have "squirrelmail-configure",
which can be run even outside the SquirrelMail installation directory). Read the documentation that came with the distribution package to find out more about OS distribution specific details.