Here is an odd one.
Have an Office365 tenant. Have created a mailbox on Office 365 directly (in cloud mailbox).
Office 365 testing shows all DNS records are Green - all entries as Microsoft requires, including autodiscover.
If I go to Office 365 webmail, i can access the new mailbox perfectly. mailflow is fine.
If i start Outlook 2016 (which is fully patched etc), it fails.
- Establish network connection - fine
- Search for email@example.com - fine
- Then it pops up a login box, but Outlook is seeing this as an Internet email
I know the DNS settings are correct and I know the user/pass is correct (webmail test)
Have tried this on multiple different machines. To no avail. Both on the domain and not.
Here is the kicker... Up until a few days ago, all working fine.