Outlook 2016 (Click2Run) Autodiscover Prioritization Issue with Office 365
A recent Microsoft update to the Click2Run version of Outlook 2016 changed its behavior by prioritizing Office 365 autodiscover over all other autodiscover methods.
This causes issues for users who do not use Office 365 as their email provider — such as customers on Hosted Exchange.
Problems typically occur when:
- The user has an inactive mailbox on Office 365
- The user has a personal O365 subscription using the company email address
Outlook prompts for login but fails because it’s attempting to authenticate against Office 365 rather than Hosted Exchange, disrupting both new and existing profiles.
Warning
This solution involves editing the Windows Registry. Incorrect changes to the registry can lead to serious system issues.
Please make sure to:
- Back up your registry before making any changes
- Follow the instructions carefully
- Be aware that Utixo does not provide support for this modification
Registry Key to Modify
The key that needs to be edited is:
HKEY_CURRENT_USER\Software\Microsoft\Office\16.0\Outlook\AutoDiscover\ExcludeExplicitO365Endpoint
Set the following values:
- Type: DWORD (32-bit)
- Value: 1
.reg File Content
If you prefer, you can apply this setting using a pre-made registry file:
[HKEY_CURRENT_USER\SOFTWARE\Microsoft\Office\16.0\Outlook\AutoDiscover] "ExcludeExplicitO365Endpoint"=dword:00000001
You can download the .ZIP archive containing the .REG file here:
ExcludeExplicitO365Endpoint.zip
