When a user tries to add a member from the global address list (GAL) to a contact group in Outlook by using a MAPI over HTTP profile, nothing is saved in the contact group list.
The problem is caused by an error in calculating the Unicode encoding string length. This error triggers an exception when the contact is being resolved, and this causes the contact save operation to fail.
To resolve this issue, install the following cumulative update:
3030080 Cumulative Update 8 for Exchange Server 2013
Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.