Office365 - CISCO Unified Messaging Service Setup

Issue:

We have a Cisco VoIP phone system and are trying to get the Unified Messaging service to connect to Exchange Online.

We are using the following guide and have followed all of the steps but the Cisco system states it is not able to manage the mailbox.

https://www.cisco.com/c/en/us/support/docs/unified-communications/unity-connection/118828-config-cuc-00.html

We opened a case with Cisco and they verified connectivity is working and they believe the issue is within O365 somewhere, we have verified that the service account we’re using is setup according to the guide and is able to login to O365 but it’s unable to manage user mailboxes.

Solution:

This case can be closed. The root cause of our inability to connect had nothing to do with MX records, domains, Barracuda or anything of the sort.

It was because Basic Authentication was disabled on our Office365 tenant.