We are at the verge of a mail server decision. We do currently use 2 mail servers : MDaemon 10 and Exchange 2003. We are planning to use a company and customer wide one point solution. Our candidates are MDaemon 11 and Exchange 2007 or 2010. We would like to learn other users experiences on those solutions. The server-side experiences, the user-side experiences, system loads, feature set, TCO, support options etc. And if there are other solutions (like MDaemon 11 + Exchange or anything else) what would you suggest ?
Edit : I would like to give our mail account numbers. We maintain nearly 40.000 customer accounts (which grows nearly by 2.000 accounts per year) and over 60 employee or system accounts. Exchange is responsible only for inhouse e-mail traffic. MDaemon is responsible for the customer accounts and is being used as a gateway for Exchange.