Outlook 2016 doesn't accept password or app password

No warning. No heads up. No notification. No communication. Notta. Nothing.

@v-bmyers,

Outlook 2013 and Outlook 2016 only support basic auth connections to Outlook.com. The Outlook Team never backported OAuth support for Outlook.com. As noted in the article the Outlook.com Team is tightly restricting basic auth connections due to abuse from some bad actors, Outlook and other apps are unable to connect to Outlook.com when using Basic authentication - Microsoft Support. There are no plans to make basic auth work better. Instead, the Outlook Team is optimizing for OAuth/Modern Auth since it's a more secure connection. Basic auth is already deprecated in M365 and will be deprecated in Outlook.com soon. The best thing to do is to move to an app that supports OAuth. A free option with ads is New Outlook which the Outlook Team is working on. You can install it on the same machine as Outlook 2013 to compare, Outlook for Windows - Microsoft Apps. Or, you could use Office perpetual or Office subscription to use classic Outlook Desktop.

I'm running 2013 as well.

While I'm certainly experiencing issues, I have discovered some oddities that may help you manage your situation.

On the "Send/Receive" tab, if you have the "Type Exchange Password & Connect" click that.
Enter the password.
It should accept it through that Feature (it usually does for me).
Click "Update Folder"

Afterwards, if you get the dialog box fired, just cancel or X it to close it.
This has happened to be thousands of times but even though I cancel or close it, mail is still working.
If you see the message on the status bar, many times I can just click it and it get the stored password and that usually works for me.

Well.... that only lasted about a day, I am back at square one again! It will not accept my credentials AT ALL today, and I cannot access email through the Office 2013 Outlook software.

I'm not sure which one of these things worked, but this morning I was once again unable to connect to my Hotmail account. I did these two things, and it has not prompted me for the credentials since!

Exit Outlook, Open Control Panel, and select Mail.

Click Show Profiles, select your Outlook profile, and then click Properties.

Click E-mail Accounts, Select your email account, and then click Change.

Click the More Settings button

Select the Security tab, and in the Logon network security list select Anonymous Authentication, and then click OK.

This option was grayed out and unavailable for me, so I went back to the Account settings window, selected my Hotmail account, then clicked REPAIR. Then I went to edit the registry to enable Anonymous Authentication that way:

HKEY_CURRENT_USER\Software\Microsoft\Office\15.0\Outlook\Profiles

Under the profile, locate and expand the 9375CFF0413111d3B88A00104B2A6676 key.

Under the 9375CFF0413111d3B88A00104B2A6676 key, you see a subkey for each account in your profile. Select the first subfolder (00000001), and then examine the data of the Account Name binary value by double-clicking the value. Repeat this process until you find the Account Name value that includes your email address. For example, ******@hotmail.com under the \00000004 subkey.

Under that subkey, locate the Service UID binary value. It represents a GUID (for example, c3 d1 9a 7b 80 1b c4 4a 96 0a e5 b6 3b f9 7c 7e).

Locate the subfolder in your profile that matches the GUID value identified and examine the 01023d0d binary value. It represents a GUID (for example, 5f cf d5 f1 ba 5c 6f 45 b3 57 cc 5e 0d 16 94 58).

Locate the subfolder in your profile that matches this GUID value identified and examine the value of the 00036619 binary value. This value determines whether Outlook is using Anonymous Authentication. 01 f0 00 80 = Anonymous Authentication, any other value represents an authentication method other than Anonymous.

FOR ME, I did not have this 00036619 subkey, so I created it with that AA binary value. No problems since!!