When running Exchange 2010 (my case SP3) make sure you install the “MAPI CDO 1.2.1 package”.
If you install this while setup was checking prerequisites, you might get an error later on while on the MAPI settings screen. Check Now resolves the besadmin account fine and changes the name to the SMTP address. But when clicking Next, you get an error.
The setup application could not initialize the Microsoft Exchange Server MAPI Client. Make sure that MAPI is installed and configured correctly and the Microsoft Exchange Server and mailbox that you specified are correct.
1) Make sure the User account is not hidden from the GAL, open the mailbox in exchange console and check on general tab.
2) Press cancel and rerun setup, it resumes from where you left off, and now it proceeds.