Outlook 2016 doesn't accept password or app password

I mean as far as your friend is concerned, that's kind of absurd, and if that was truly the only reason the relationship ended, that's someone you don't want to be involved with anyway. Do they not have phones to call each other? Text messages? Email is far from guaranteed delivery, we take for granted that it is reliable but stuff sometimes goes wrong, gets sent to spam (or blocked before even hitting your mailbox), etc. I think he dodged a bullet honestly.

I've missed work and client meetings due to email issues (on their end or on ours), nobody got fired.

It's not my place to judge my friend's girlfriend or their relationship. I know plenty of very busy people live their lives through Outlook/calendar, so I can relate to my friend. I work 14 to 18 hour days, travel constantly, so I, too, live off my calendar... If this is an one-off issue, perhaps she should be more forgiving. However, you are forgetting this has lasted 4 weeks now! What mission-critical infrastructure in our lives would have down-time this long? Imagine your internet feed at home, or your mobile phone, or your electricity service go on and off throughout the day for 4 weeks... Let's see if you miss a meeting or two, 4 weeks in a row, and see how that fare for you at your job.

This issue is certainly frustrating, and I'm seeing the exact same thing I see at my job, development and support outsourced and fixes, even to stuff far more critical, take weeks or even months to fix.

That being said, it has not been "down". Webmail (accessible via phone browser) has been fine, albeit inconvenient, and bouncing network or cancelling password prompts has worked for most.

They need to fix it, they need to roll back whatever they did, but honestly even with 49 pages of comments here, my guess is the impact is to a small percentage of their user base. Large corporate clients are their main concern, and only ones that aren't using modern auth correctly (which has been required since last year) seem to be impacted, at least from what I've seen here.

I guess it is a good illustration of how reliant people are on email as a primary means of communication, and they forget that there is good old fashioned talking to the other person.

Had email for work been down for even a few days and people were missing customer meetings, the only people facing termination would be those responsible for the email infrastructure. The rest of us would have found a workaround, even if it came down to writing on a physical calendar (but I'm confident they'd find a better workaround like telling us to stay logged into webmail and web Teams).

A small update from my side too:

A few days ago, the error only seemed to occur when I changed the network (WLAN, mobile network) and thus the IP. Now, however, the connection is unstable even after some time on the same network.

For example, for two days I always had the error after the forced resconnection of my private Internet connection at home. Now it also happens during the day when definitely no new IP address has been assigned.

I also confirm that several attempts (clicking away errors and synchronizing again) eventually lead to success, so I also assume that it is only due to certain Auth servers.

In general, I thought it has become a bit more stable in the last few days. Unfortunately, this is not the case.
I have also noticed that even with a working connection (i.e. no password request), some of the mails are not pushed, but are sent collectively after some time. This could also have something to do with the problem, so I'll mention it here.

Edit: What I did not mention here is: I use BlackBerry Hub+ Services and my client supports both, EAS and EWS connection.

Edit2: Just to test I deleted the account and tried to set it up again with new App Password. First witih autodiscover and EAS, no way. Even after 20 tries. Then with "manual settings" and EWS, no problem to set it up.

I will monitor when I will receive the first password prompt error and give you feedback here.