NEW Outlook app: how to add an IMAP account with user name different from email address?

You are right! I also can't understand why the new Outlook doesn't support IMAP - unbelievable!

But just using classic Outlook (Outlook 365) solves your problem.

Just adding my shared frustration on this subject. This going to stop me from using Outlook as my IMAP email client completely, quite soon.

Plenty of other options exist of course (Thunderbird is my personal choice), but, it's the integration with family calendars, To-Do and other MS services which makes this such a pain. And for something so, so simple that it should have been in the very first release.

We really shouldn't need to be making a feature request for this. It's a very disappointing experience.

Are there some versions of Outlook that include this functionality?

I can, at least, answer this part for you: Outlook 365 aka Outlook Classic - includes it.

This is currently how I'm accessing my IMAP account on my Windows 10 PC. Since my Windows 10 installation will end of life in October, this solution works for me for now.

However - according to Microsoft - they want most people to transition from Outlook Classic to Outlook New by April 2026:

Microsoft's plan is for the entire transition over to the new Outlook app to be completed by April 2026, but “existing installations of classic Outlook through perpetual and subscription licensing will continue to be supported until at least 2029,” said one Microsoft representative who reached out to us.

from https://www.pcworld.com/article/2551776/classic-outlook-gets-an-official-death-date-microsoft.html

If Microsoft is following this thread, we would appreciate a comment on whether this issue is expected to be addressed, or what solution you recommend. Are there some versions of Outlook that include this functionality?

Thank you, Andrew

might be true. I was only referring to Classic. Sorry for not specifying