Mailserver has been setup using postfix,dovecot,mysql,postfixadmin and squirrel mail. Is it possible to forcefully make an user change his password after certain days and also send an alert email along with the link to change the password.
Is it possible to forcefully make an user change his password after certain days?
No. As far as I know the common mail protocols (POP IMAP) don't support a password change mechanism; the password either works or is doesn't. So you won't be able to that for users using regular mail clients.
Webmail would be an exception, because that is almost guaranteed an interactive user session, but even that it would be enforced from the webmail software and not the mailserver.
Send an alert email along with the link to change the password?
Of course, if you have a web front-end to a password manager you can easily script such a thing.