I haven't worked with Mason but I know a bit of what it does and it seems you want more integration into an existing website. I don't have any expertise with performance between perl and php so I can't comment on that :)
The only other thing I can add to the conversation is my interest in looking at imapproxy or something similar to allow caching of imap and improve web client performance. I haven't tried it yet, but it's something I'll goof around with.
i thought squirrelmail would be way too much of an overkill for my needs also but i went for it. i'm using debian and i got the squirrelmail
easy is that squirrelmail comes with a configuration utility (squirrelmail-configure). it was very easy to get things configured without worry about a lot of conf files :) i also like the many
Dan Wang wrote: package installed and working within 15 minutes. what really makes life plugins
that people have created for squirrelmail. it's also very simple to add these plugins into squirrelmail using squirrelmail-configure. i had originally been ssh and mutt to check my mail, but i decided it be nice to have a web front-end and squirrelmail /apache /dovecot /procmail /spamassassin /gotmail /getmail /fetchyahoo have been a good mix for me. the hardest part for me was figuring out procmail and not squirrelmail :)
squirrelmails nice. I'm not going to knock it. In fact, I consider it right to be an example of what to follow.
But my interests are to write something for compatability with mod_perl and HTML::Mason so give me a system that will be much faster than squirrelmail and easier to include in web sites. (HTML::Mason would allow you to write the entire webmail application as an object to include in a page...) The advantage of HTML::Mason over PHP is that it's very easy to cache pages in addition to the advantages of mod_perl over PHP (unless you use Zope?).