Outlook 2016 doesn't accept password or app password

The issue is still random and have different patterns for different people. I am in Asia and Android EAS is nearly not usable and worse than when I was in the US. I moved some of my data to my Google account and things are incredibly smooth, even over roaming data. This move will backfire for Microsoft in the long run. They are doing all this to capture more users but then you have long-term customers like me that are so put off by this, it actually drive us away.

yes but my Hotmail account does not work with the new outlook app !

Gabriel,

Perhaps I'm missing something already written before (I'm not about to read and study all 76 pages of this hideous thread), but I begin to wonder if the issue here is LESS about your servers and more about how our Apps (Outlook 2013 and Outlook 2016) are dealing with messaging from your servers.

To refresh, I'm using OL 2013 with 1 (one) hotmail and 3 outlook accounts.
Like everyone else, I keep getting the password dialog boxes being fired.
However, the password dialog box being fired IN NO WAY means I'm not connected.
It might mean that, but usually this is only after some length of time has passed since I took some corrective action.
And by corrective action, I DO NOT MEAN ENTERING THE PASSWORD IN THE DIALOG BOX.

For me to come to this possible conclusion it's important to remember all these messages are being managed by my application (Outlook 2013).
These messages (dialogs boxes or status bar prompts, or ribbon buttons, or Windows alerts) are ALL being triggered by Outlook 2013.
NOT YOUR SERVERS.

AND, when I follow certain steps (within a reasonable time frame) I remain connected to your servers DESPITE the messaging from Outlook or Windows.

When I'm selected on one of the 4 accounts, and the "SEND/RECEIVE" Ribbon has the "Type Exchange Password & Connect," (and the status bar says "NEED PASSWORD") if I click "Update Folder", it updates and the "Type Exchange Password & Connect" button goes away and the status bar changes to "CONNECTED TO: MICROSOFT EXCHANGE". And this process will work regardless of whether or not Outlook fires a PW dialog box until or unless I go too long without clicking "Update Folder" (such as over night).
But in the morning, if I get the PW dialog when I click the "Update Folder" button I just enter the PW one time and I'm back to being connected for the rest of the day (regardless of if or when I get the PW dialog boxes again or how many times I get them).
Actually, the only exception to this is on one of my Outlook accounts the "Type Exchange Password & Connect" doesn't go away until I click it.

But AGAIN, this is ALL being managed in Outlook. NOT ON YOUR SERVERS.

Which brings me to the prospect of a solution (or probably why there is no solution).
The solution is not and cannot be on your servers.
At least, not until or unless you configure your servers to send the messages our applications expect so they'll quit freaking out.
I wonder if there is or might be some reg keys we can edit or add which will enable our applications to stop freaking out or to disable the freak out mode.

I know MSFT's messaging has been that OL 2013 and I think OL 2016 are out of application support but we may still get security updates (I think).
I can't help but think a "security" update to add interaction with our registry to disable our applications from freaking out, or to enable them to manage it more appropriately might make this go away.

So yeah, this isn't my first rodeo with MSFT ( I used to work for MSFT years ago) so I know what I just wrote is an exercise in futility.
But I mention that because absent that happening, MSFT ought to be a bit more honest about what's really happening here.
It seems CLEAR to me that MSFT has changes it's server responses and these responses are trigging our applications to freak out without regard to our actual connection status. Further, MSFT is unwilling or unable to return to the old responses or add the old responses to the new responses or to provide an update to our applications to manage or disable the freak out episodes.

What Outlook app are you using?
I have my hotmail account installed on the free Android Outlook app and it's working fine.

My only issues are on my PC with Outlook 2013.

Outlook for Android doesn't have the issue. People don't want to use it because it's not just an email "client" but rather a data scrapper for Microsoft. It will access and take all your 3rd party data from non-Microsoft sources, including data you have from other non-Microsoft account synced on your phone, and not just non-MSA you added into Outlook for Android. You can think of Outlook for Android (or IOS for that matter) as a data gathering gateway just like how Facebook access your contacts, search, location, messages. Microsoft is doing the same by masquerading all of that efforts in the new Outlook family of apps, which includes Outlook for Android, Outlook for iOS, Outlook for MacOS, and the "new Outlook" for Window The MS employees here are sensitive or dismissive to these concerns, but most people do care. The EU government is looking at this as well.

The issues people are having is using EAS protocol to access Hotmail accounts by using device's native email client, i.e., GMail for Android or Mail for iOS. MS is messing with the EAS protocol authorization method, or that Hotmail accounts does not support OAuth as suggested. For EAS on mobile, you just don't have any access at all if you are hit with the password prompt. Basically, you are locked out during that time. MS already said that they added some code to guard against brute force attacks and their code misidentify our legitimate access, so it blocks those authentication attempts hence you are getting credential prompts.

People are also having issues with older desktop Outlook, basically 2013, 2016 and 2019. The only version works is 2021. In this case of older Outlook versions, people can dismiss the password prompts and sometimes Outlook will stay connected and sync emails and other data. Outlook desktop seem to establish multiple data sessions, so even if you cancel the password prompts, it seems to have some sessions alive enough to still sync some data. Some days, you get a ton of those prompts, and even if you can dismiss them, it does become a headache and distraction.

People are then also having issues using with EWS protocol and those are 3rd-party desktop email clients. This is similar to EAS in that once you are hit with the issue, you can't connect at all when the server is blocking your authentication attempts.