Outlook 2016 doesn't accept password or app password

Please let your developers know that the people with 2FA/MFA setup are also having the issue.

Based on experiments over the last few days, I think there are multitude of issues at play:

1. Possible authentication/security related issue on the server-side - it sounds like the team has improved or at least they thought they fixed the issue.
2. Code changes related to 1) has not propagated to all servers and it has been several days, so one would expect those code changes should have reach all the key servers.
3. Still possible issues related to IP address changes. I have noticed an increase in password prompts when I transition from 1 IP address to another. Scenario is:

a) leave office (one IP address) and transition to different IP on the mobile network - this surely will cause prompt(s)

b) enter hotel and transition from mobile network to another IP address of the hotel's - this will likely cause the prompt(s)

c) hotel WiFi may disconnect, so the device momentarily fallback to mobile network - this could cause prompts.

In my case, office IP address and hotel IP address are the same, so I do not see the security risk here. I also not introducing new devices onto my account, so the known/assigned UUID to the device should provide some level of assurance. Competing platform does not have such issue with their email accounts. And to be blunt, this seems like a design issue not to factor into consideration of these very likely network transitions.

In short, either the fix has not reached all servers or the fix still have weaknesses against real-world scenarios.

Your comment is very limited in scope and ignore obvious facts. There is no such thing as "free" product. In this case, we paid Microsoft through the Windows OS license that is part of the device cost - it's not free. The Outlook clients, that we are having issues with, is also a paid product - it's not free. Hotmail/MSN Mail/Outlook mail is a free product but they use it to mine data in our emails and place ads. It's also not free, just paid differently.

If Microsoft does not want to make sure these run smoothly, i.e., I get 5-10 or so email on my personal account, versus 100-300+ a day on my work account, then Microsoft can exit the consumer market. Email is now becoming a critical part of our daily lives, it need to have certain level of care and reliability. I am not expecting 99.99999999999% up time for consumer products, but an issue of this severity and impact, effecting multiple email clients including Microsoft's own, lasting almost 2 weeks, is somehow OK to you is just mind-blowing...

The company I work for is using Office 365 for Business. I have a supplier/partner account with one of my customers that is on Google Workspace. The amount of issues on Office 365 is so alarming that I am talking to our IT about switching. Google's stuff just humming along with zero issue. So much so, I sometimes send myself a test email to see if the account connection is still alive - and it is.

With Office 365, if it's not password prompt, it's that stupid 2FA/MFA prompt that has a "...don't ask again for 365 days..." box. Even checked, I get the prompt at random well before 365-days is reached, even before this current issue. These are critical accounts, so I have very secured randomly generated passwords and I don't have the password manager on my phone, so every time I get 2FA challenged out of normal, I can't address it until I am back near my computer. If it's not password issue, it's sync issue. My calendar and contacts are not auto-sync'ed, even though the setting is set to auto-sync. Again, no issue on Google. The moment I add a calendar or contact, it's on my phone within a few seconds. With Office 365 and working EAS connection, I have to manually go to the account setting and force it to sync to get updates.

I travel constantly for work and Google challenges me the same way I expect it should - when I go to far and random places that I never go to. With Microsoft, it's so stupid that it's beyond words - always challenge me at my foreign office, or the same hotel I've stayed at for years, both of which has fixed IP addresses. When I go to some random places where I think it highly risky, MS doesn't challenge me.

If you also look at spams, vast vast majority of them are transmitted on Microsoft infrastructure from Russia and East European spammers. Microsoft seems to have no way to stop them effectively. Ironically, I have gotten a lot less Microsoft-originated spams on my non-MS accounts from since this current issue. At least there is one little benefit out of this whole mess - spammers probably have a harder time to send spams.

Outlook 2013 need to be at least at version 15.0.4971.1000.

I'm using Outlook 2013 version 15.0.5603.1000

2-steps verification is On.

Using app password.

Outlook still prompted for password, and would not accept new app passwords (as of 02/06/2024 ~ 1PM PST).

In fact, it is not resolved for third party applications using EWS or EAS on personal accounts. Even with 2FA swiched on and App password it is not working, it continues prompting to insert password.

I was able to sync once yesterday by changing from outlook.office365.com server to m.outlook.com server, after that I swiched back to outlook.office365.com and to my astonishment this worked. But after some minutes it shows the password prompt again. And it was with App Passwords.

Again: This is not resolved.