Exchange 2013 OWA and Activesync Working but Outlook cannot connect

Hello all,

We are in the process of migrating from exchange 2007 to exchange 2013. This has gone relatively smoothly.

I have setup 2 CAS servers and 2 mailbox servers.

Owa and activesync are working great internally and externally. However, my outlook 2010 client will not connect to the exchange servers.

It is successful in :

Establishing network connection
Searching for "user" server settings

Unsuccesful in "logging into server".

Error is: The action cannot be completed. The connection to microsoft exchange is unavilable. Outlook must be online or connected to complete this action.

the final step.

I am relatively certain this has to do with either the URL or the certificate (which is internal CA signed). we will be getting a 3rd party certificate soon.


URL setup for virtual directories are as follows:

Internal url: ex13-cas-a.contoso.com
external url: webmail.contoso.com

Please let me know if i can provide any additional information.