Syncing emails from user to user

First make sure Squirrelmail is set up correctly, using conf.pl (which you should now have). It also can manage Plugins. I myself don't use Squirrelmail any longer, so I hope someone else on these forums can take a look as well.
 
Squirrelmail is just fine, and you appear to need to manage users, passwords and such, with plugins. I use RoundCube for myself only. It's not as advanced as Squirrelmail yet (still alpha/beta, no user management or plugins), but it suits me just fine when I can't use straight IMAP.

Just continue with Squirrelmail, and make sure you configure it the way it should be done. It's not rocket science.
 
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