Especially if the Outlook version is not up to date (Outlook 2010 and older). You may get a support call soon.
I got my support call earlier this week as email stopped working on both the laptop and desktop (although the phone was OK – in fact that’s how it was reported to me – My email’s not working anymore except on my phone – help!!)
Recalling the migration of the platforms to Microsoft Office 365 I wondered if that was the cause. But first logged in remotely, checked things were broken as reported (there was some confusion between OneDrive and Outlook not working) – always check the problem is as described!
It was definitely broken, and reporting connection errors. Inspecting the Account settings the accounts were connected by MAPI (the old method).
Anyway, creating a test outlook profile proved that this was the issue. However, you cannot change the source of the account in the existing profile. So for this support problem, I added the original accounts (there were two here, outlook and Hotmail .com) and then changed the default account, and then deleted the old ones.
Of course at this point the OST files with all the email go, and you are back to downloading the entire account history from the backend servers. Fortunately in this case the connection was fast and took a couple of hours across both computers.
It’s a bit of a shame that Microsoft didn’t email account holders with a notice to say that the underlying account was being migrated to say the least. A warning email should really have been possible with (say) 4,2, and 1 week to go. Instead it just suddenly breaks.
It’s also worth checking the recovery account details – in one instance the recovery was to an old email account that was from a cancelled ISP account. That was swiftly sorted ! Go to “account settings” (under the avatar for your account top right on the web page), “security & privacy” and “more security settings” and look for:
Also – note that according to https://www.howto-outlook.com/howto/outlookcommigrationinfo.htm#outlook2013-2016 it is still advisable to change your email settings, even if you are on the latest and greatest (at least it carries on working though).