Microsoft recently released an update to Outlook 2016 called Direct Connect to Office 365.
This update is causing connectivity problems for some users to our Hosted Exchange service.
Symptoms involve the inability to send email, sent email being returned with the sending address showing as a long outlook.com address or the inability for Outlook to open its folders due to a login error.
To fix the issue please do one of the following...
1. Download the attached registry file and double-click it to have it add the two registry entries needed to prevent this behavior. (Recommended)
2. Follow the instructions below to manually add the registry entries yourself...
Manually Add the Registry Entries
If Outlook continues to exhibit issues, you will need to create a new Outlook profile and have it sync with our services.