Looking for a linux OpenSource mailserver

I am looking for a opensource mailserver that intergrates with M$ Outlook and hase the ability to share the calender/agenda to have 1 agenda for all the user to see and add events in but at the same time have there own agenda and apointments that partly overlap into the shared one. i think its called grouwise or something like this?

I know that Kerio hase one but thats 500-600 dollars...
If any one has a sugestion..

Dimmy

The outlook integration for calendars is the tricky part. Virtually all of those are commercial plugins. I looked for a long time for a client that "had" to have one before finally realizing it was not feasible at the time.

Yes its the integration. If you want good integration most packages will cost.
For a good free mailing program its worth checking out http://tincan.co.uk/?lid=453, I dont know if it has any option for outlook

Another free mailing list program is Dada http://mojo.skazat.com/features/

May help you, may not

Thanks a lot will check in to that

When I was looking for openExchange alternatives I came across this page. It puts the matter in a nutshell. I liked the ’mule comparison’.
http://expertanswercenter.techtarget.com/eac/knowledgebaseAnswer/0,295199,sid63_gci972524,00.html