SquirrelMail doesn't store any passwords. It's the IMAP server's responsibility to take care of that, and

the IMAP server can choose from a number of different backends, such as SQL or LDAP database for

instance, to perform that task. Fortunately, there are several SquirrelMail plugins that, depending on

how your system is set up, can be used as a change

password interface.

It you're using SquirrelMail 1.5, try the included change_password plugin first. If it doesn't work, or if

you're running some other SquirrelMail version, try the plugins at the change password plugin page.