We went through a reputable consultant lead migration from Exchange 2003 to Exchange 2010 about a month ago. I will do my best given my skill set to explain what's happening. All is well with the majority of the 40 or so supported. However, as far as I know, at least 5 or six people (including myself) are getting repeated authentication dialog boxes from Outlook (a mix of 2007 and 2010 users). In addition, we have seen some issues when trying to access Out of office alerts from at least one Outlook 2010 user. It's my understanding that these two issues may be related somehow.
Our consultant came out and re-keyed the certificate - adding all the possible server names - reinstalled the new certificate (two of the three are currently listed as "invalid" amongst the one valid one) and he also configured auto-discovery - thinking that these steps would eradicate most if not all of the problems but they are still present. For what it's worth, I didn't see a single pop-up dialog box today until I broke connection with the email server over a remote desktop session. I've received two re-authentication requests from Outlook within the 30 minutes since breaking the connection.
We called in a different consultant to look at the problem with fresh perspective and he seems to feel the issue lies somewhere within the auto-discovery configuration.
Any all help is appreciated. Thanks.