We are running Exchange 2016 on Server 2016. After we were informed by Microsoft that we needed to upgrade to CU19 we installed it on the same day.
Unfortunately it broke our ApplicationImpersonation account that was using the Administrator account. Specifically it has broken a program called Mailstore.
Mailstore Support said they were confident Microsoft would fix the issue in CU20 but this hasn't happened. We installed CU20 (15.1.2242.4) and rebooted the Exchange server and the problem still exists.
Mailstore Support said that a work-around would be to create a new ApplicationImpersonation as a lowly user, but I have created the account and assigned it the ApplicationImpersonation role, but Mailstore (the program) just says that the credentials were rejected by EWS:
An error has occurred.
Authentication failed (EWS). Check user name and password. If the password is correct, try specifying your UPN Logon (e.g. user@domain.com) or DOMAIN\username in the user name field.
I have tried different username formats but all are rejected.
Interestingly Vipre Email Security seems to be working fine, but it was set up with ApplicationImpersonation as a lowly user from Day 1.
Has anyone else seen this? Am I barking up the wrong tree? Any ideas how to get ApplicationImpersonation to work?