Outlook 2016 doesn't accept password or app password

What I'm wondering about is the very different behaviour on different devices with the same outlook.com account:

• on Win10/OL2019 and Win11/OL2021 there is no login problem
• on iOS I have to repeat 2 or 3 times
• on a Win11/OL2019 machine it's nearly impossible to login regardless how often I repeat the login.

It is not surprising to see different behavior in different clients with different configurations. Each client may be sending the password in a different way. I'm referring to the timing of the requests - how rapidly and repeatedly the client sends them to the server and in what order. In any event, it's probably not a straight up authentication failure; even while we are pounding the password in there is some connection going on in the background, to which different clients do indeed seem to act differently. another factor might be how quickly and cleanly each client releases the account.

To your point, when I configure an email account in MS Office 2021 Pro Outlook as IMAP and compare it to the same account configured in the same installation as exchange and compare to other clients:

• In MS Office 2021 Pro Outlook when configured as IMAP there are repeated pop-up requests for the password until it finally goes through or is canceled by the user. Frequency of occurrence is variable as described in my previous post.
• In same MS Office 2021 Pro Outlook when configure as Exchange, different pop-ups occur less frequently, but the status bar reports a disconnected state even as email is coming through.
• In same email account configured in the Thunderbird as IMAP the symptoms somewhat resemble IMAP in Microsoft office 2021 Pro Outlook but with slightly less frequent password requests.
• In the same email account configured as IMAP in Fair Email on android the pattern also resembles the repeated requests for password that occur with IMAP in Outlook but the method for refreshing in the UI is different.
• On android in Microsoft Outlook app no errors are presented but that renders itself not viable for troubleshooting by being so heavily proprietary and obfuscating our ability to check settings and troubleshoot it. I smell a proprietary rat.

On your Win11/OL2019 machine what client? IMAP, POP, Exchange?

Exchange

Exchange

Interesting, our setups are somewhat similar (Win11/OL2019 : Win10/OL2021). Maybe that (more severe inability to connect) is related to the status indicator showing "disconnected" that I see when an account is configured as exchange.

In addition to the differences in behavior between different clients and email types there might also be differences in what different people experience, based on region (eg routing issue) or based on what servers the account data is stored on (server maintenance or recovery)...or something like that.

In any event the issue persists. Thanks for the details. I'm glad to know the issue is no in my gear.