we are a small business company (60-100 emploees) handling financial data. We want to have a secure E-Mail Server. What is the best in-house solution? Our laws force us to ḱeep the server physically at our place. Is Exchange secure enough, or are we better off with Linux and Postfix+Dovecot? For that reason we will hire a system-administrator, but whats more secure solution? Thanks in advance
Unless you really need Exchange, I wouldn't use it; I mostly base that on cost. These days there are enough alternatives which work with whatever client you like for full calendar/contact/email integration. Of course if you already have most of the Microsoft and Outlook licenses, Exchange doesn't cost too much more.
If you just need email, postfix and dovecot are fine. Personally I use exim and cyrus.
You can also look Zimbra for a complete solution.
Exchange 2010 is pretty easy to implement, it is very secure and I never heard of someome hacking into exchange, the one thing that is really important is your router - only port 25 is open to the outside world. Most companies has solutions with exchange integrations and you probably also want to have emails/calendar/tasks working withyour blackberry/iphone, Blackberry Enterprise Server is working well with Exchange.