Outlook 2016 doesn't accept password or app password

Note that outlook.office365.com, eas.outlook.com, m.outlook.com, and s.outlook.com are all just aliases for the exact same thing.

From what I've observed when this was happening (has been fine for 2 days for me now), it isn't the settings themselves that make any difference, just the fact that when you change the settings, you disconnect and reconnect, get a new randomly assigned server, and often times that is one of the working servers. Same when flipping between wifi and mobile data etc.

You're actually overcomplicating it. You don't have to use the account to log into windows, you don't have to log into edge. You just add the account under "email & accounts" in windows settings. You can then choose to use that account or not for various things. Outlook detects it automatically.

But for work, if you work for a large company, I don't understand how they would allow an offline/local account to authenticate you to company resources. So like I said, the authentication structure is flawed, if you do not want your MS account known to anything except outlook, then yes you're going to have to hack things a bit and your credentials will be lost from time to time after updates or every x days.

MS for better or for worse has moved to the ecosystem model, which is why they've made it so difficult to use an offline account in windows. As far as they're concerned, you should be using your MS account to log into windows which then will authenticate you to things like email, onedrive, optionally edge, and if your company is modern managed, your domain and resources as well. Apple and Google started the trend, MS jumped on board. Same with forced updates.

But then in the same message you say your phone is logged into your google account (which you don't really have a choice, not if you want to actually use most of the features of the phone) - so why no paranoia there? It is possible to use your phone without a google account, but it will be inconvenient and glitchy, exactly what you're seeing with MS.

Not just the same password, but the same account, tied to your windows login or added to windows. In my case I've never seen any prompt or authentication to add the account to outlook (or at any point after), it just adds, pulling from the account info with the modern auth process that was validated when added to windows. I don't even sign into windows on my personal machines using MS account (I prefer a local account), I just added it to the additional accounts in windows. On work machines the login to the machine is a MS account (using our company's domain and custom modern auth screens) so that takes care of it.

From what I've noticed on my Gmail android, it isn't that sending an email or synching causes the issue, it is that the issue exists and that's what makes it realize it, it can't complete the action, and that's when the "credentials required" comes up. Or it also comes up on its own after a while even if I didn't try to do anything. Bouncing the network usually resolves it.

Today so far, multiple changes of networks and IPs, IPv4, IPv6, all working fine on Gmail.