Mail Server With web-based access
 

I have read through the fourms and have not found anything about a good easy to use linux mail server with a web access. I have about 200 people using our current exchange server. We need something fast and reliable. each user get about 200-300 emails a day so something that can hold up. Also the web feature needs to be easy to use. Any suggestions

Personally I would reccomend:
SMTP: Qmail
Retreival/storage: courier-imap
webmail: squirelmail
advanced webmail and calendaring: moregroupware
Address book and authentication: openldap

For webmail, also give Horde/Imp a try. It has more features than squirrelmail and you can add other modules to it (calendar, addressbook, etc)

Personally I think squirrelmail is great for webmail. Plenty of customization options and many plugins available from their site including SSL auth, calendars, group calendars, weather forecasts, etc. I have not used Horde/Imp so I cannot speak for it.