This seems to be an exchange lookup issue but it looks correct. We have Exchange 2010 on site and the icadmin is the only profile set for the outlook client and mail settings. when we go to create a user, it will not allow a lookup of the email either. This is causing an issue as the voicemail is attempting to resend 10 times then fails but, other users like mine, work just fine. seems odd that if it uses the one account for mail and AD access that only some would work.

If you are CIC 3.0 SU 15 or higher, then switch to using EWS instead of MAPI as it is less likely to have the intermittent connectivity issues.