Outlook 2016 doesn't accept password or app password

Perhaps I should mention that my private account @outlook.de (outlook.com account) is added as guest account to an organization. Normally this is done by creating an alias within the organization which is something like "*** Email address is removed for privacy ***" and policies are set for this alias. I only have to log in to my outlook.com account, verify with my authenticator for this private account and then verify again with my authenticator for the organization account.

I do not get E-Mails via this alias at all, so its only to sign in to their teams. Also the auth problem is only with my mobile devices third party app trying to connect via EAS to my private account, not to the alias, also with app passwords enabled. But perhaps it has something to do with that.

By the way: Since app passwords are only shown once when they are set up, it is really annoying when having a new password prompt since you have to generate a new app password just to get another authentification failure...

From not the community crew:
If the client is modern authentication ready, if the really old EWS function works? (Personal account EWS method?)
h t tp s :/ / as k u b u n t u . c o m / q uestions/109548/evolution-and-office-365
Host URL: https://outlook.live.com/EWS/Exchange.asmx
OAB URL: https://outlook.live.com/OABThough

The *.office365.com,  *.outlook.com, pop3.live.com, *.hotmail.com, outlook.live.com seem to have numerous ipv4 and ipv6 IPs in the d n s c h e c k e r . o r g

The imap.live.com, imap-mail.live.com, pop.live.com, smtp.live.com, smtp-mail.com, eas.live.com are mostly the same 204.79.197.212 or 2620:1ec:c11::212 from most dns in the d n s c h e c k e r . o r g

It recalls me that if the IPv6 affects since the webpage of outlook.live.com have several third party MS owned website and some are ipv4 only, some has ipv6.My ISP is dualstack but sometimes it will be only ipv6 or sometimes IPv4 only at first or lost one of them after sometime.

Mine is not fixed.

If there a Microsoft account contact page that we can get instructions on how to resolve.

This is more that silly. Over two weeks

I just was able to set up my account again, but not as EAS but as EWS account, and only via mobile network, not via WLAN.

It seems that for some reasons some IPs got banned or blocked by microsoft for some time. Could be that it takes some time to get them unblocked again. I think this could be due to too much authentication failures from this IP...

This are only guesses from my side. At the moment, my connection works again when only in mobile network. Whenever I swich WLAN on I get the password prompt again with authentification failure.

I was able to set up the account via EWS with 2FA enabled and app password.

I will try to set it up again with EAS and in WLAN tomorrow or the day after

From not community member:

Since most mobile network have private Ipv4 (Same or some IPs shared by many devices), and may have public IPv6 ,but the same or some prefix among the devices may be treated as the same one by some service. The mobile network should behaves similarly alike the Home gateway WLAN.

Does the mobile network and WLAN have the same ISP or same dns? which may route to the similar range of ips of the MS server?

How about the wellknown public DNS such as google, cloudflare, quad9, and etc?

And suddenly wonder that if the Microsoft Exchange addin would be affected by the MS edge webveiw2? such as the DOH setting in the MS Edge.

https://learn.microsoft.com/en-us/office/dev/add-ins/concepts/browsers-used-by-office-web-add-ins