The best replacement for microsoft exchange server is kerio mail server.

The best alternatives to microsoft exchange server are rated as following:
★★★★★  kerio mail server
★★★★★  zimbra

Your alternative for microsoft exchange server is not listed? Suggest!
Speaking about microsoft exchange server, one probably shouldn't forget about outlook.

Other search terms related to microsoft exchange server and their ratings are:
★★★★★ outlook
You have in mind a companion for microsoft exchange server and it is not yet here? Propose!



Google Trends

Scale is based on the average worldwide traffic of microsoft exchange server in all years. Click on graph for more.
microsoft exchange server
kerio mail server
zimbra