Recently one of my customer tried opening Outlook and it thrown the following error:

Outlook Connectivity Error

During troubleshooting we noticed that the OWA works fine but problem while accessing Outlook. This happens because he still using the same profile and the mailbox was recreated some time earlier.

In this scenario, i recommended him to delete the existing profile and create a new one like (Control panel-> Mail-> Show profiles...-> remove existing profile ->Create new profile). This resolved the issue and helped him to move ahead.