I’m helping a customer move a domain with a few mailboxes from one Office 365 tenant to another. After setting up the domain in the new Office 365 account, we got email flowing immediately (verified by logging in with OWA), but we were unable to set up Outlook pointing to the new tenant.
If you try to add the Office 365 account to a new profile from the Mail applet the Control Panel, you may see this:
If you try directly from Outlook, this happens:
The message “An encrypted connection to your mail services is not available” takes you to MS KB2989972, which suggests running the Outlook Connectivity Guided Walkthrough. Apparently that tool no longer exists (not found error), but the helpful Microsoft Support and Recovery Assistant for Office 365 tool can be downloaded here: https://diagnostics.outlook.com/. Running that tool confirms what I suspected, that there is an Autodiscover issue:
Oddly, after running that tool, one user was suddenly able to connect, but the other two were not.
Microsoft Support suggested running some commands to reconfigure Autodiscovery on the machine:
REG ADD HKCU\Software\Microsoft\Office\16.0\Outlook\AutoDiscover /v ExcludeScpLookup /t REG_DWORD /d 00000001
REG ADD HKCU\Software\Microsoft\Office\16.0\Outlook\AutoDiscover /v ExcludeHttpsRootDomain /t REG_DWORD /d 00000001
REG ADD HKCU\Software\Microsoft\Office\16.0\Outlook\AutoDiscover /v ExcludeSrvRecord /t REG_DWORD /d 00000001
But that made no difference, even after a reboot.
I tried adding the mailbox to my own Outlook, to test it on another machine, but that didn’t work either.
Support says that propagation may take up to one day. So I guess we’ll try again tomorrow.
Update February 16, 2019
Sure enough, the next morning, Outlook was immediately able to connect to the mailbox at the new tenant. Seems that once you confirm it is an autodiscovery issue, it’s best to just wait 12+ hours and try again.