Outlook 2016 doesn't accept password or app password

One thing I'm getting from this whole saga is that proprietary protocols are bad. IMAP, POP3, SMTP, CalDAV and CardDAV are all well supported open protocols, and if every email server made them available, the amount of breakage within email clients would surely be lessened.

11:28 AM CST. Authentication error. Could not sign in. Outlook.com account using eas server and 9Folders email client. Obviously still not fixed.

A bit more luck for me. I could not connect to eas.outlook.com or m.outlook.com on my main phone in the last few days. I have tried many many times on my phone + 2 other Android devices, but no luck. These have stock Android 12, 13 and 14 environments. Every time I add it as Exchange account type at the OS's account screen, I would get "...cannot connect to server...contact your IT..." error. I repeatedly submit add and it would keep getting the error message.

About an hour ago, I was suddenly able to add the account back with no other changes, on all 3 devices after 2.5 days of attempts. Sync of emails/contacts/calendar all worked. Now, here comes the interesting part. In Android account entry for the added Exchange account, there is a "Server settings" section near the bottom. Under "Incoming settings" selection, your account related settings are all listed. At the very bottom, there is OS option called "Switch to modern auth". This appears to be conversion option without user retype the credentials. Once I click this, a browser session is launched, similar to normal OAuth login screen. I would error out at this point after multiple attempts. If I abandon this, the account remains working.

I then retry the same process with my work account. Initially manually adding it, so it would be Basic Auth, then I use the same "Switch to modern auth" and is able to successfully convert to Modern Auth. This show this conversion function works. This goes further to strengthen the argument that EAS with OAuth may not be supported or is not currently working correctly for consumer email accounts such as Hotmail.

Hi, I am one of the many regular readers of this post, which has remained silent until now. I am a 365 subscriber with family plan and all members so far have used the Microsoft account as a reference for email, contacts and calendar synching. We all have Android smartphones and for all of them I had set up an EAS account on the system side (Gmail) with the instructions provided directly by Microsoft. Only this action allows you to use native/Google (or third-party) apps dedicated to calls/contacts/calendar without problems. I use the outlook mobile app exclusively to manage emails, because that's the only way I think it's useful and I prefer it to Gmail. I've been struggling with these problems for a month and I'm afraid that in a few months, when it is decided to completely end support for basic authentication, I will be forced to migrate completely to the Google ecosystem, despite having a 365 family account and lots of emails hotmail/outlook.

Microsoft, please, analyzes the problem again: many people don't just want an IMAP account. We want, even for the consumer, an EAS (or replacement, the important thing is that it has the same utility) account to synchronize everything, including contacts and calendar. The problem is described perfectly in this AnotherBug post to which I'm responding.

Are you really sure that OAuth works well with the EAS protocol even for consumer users? Really the problem, in my case, would be Google not updating its app to fully support OAuth, despite it also being a company that is naturally pushing towards modern authentication? Even in the solution examples regarding Thunderbird and Apple mail, it seems to me that it's always and only the IMAP protocol.

As a further starting point for analysis, I would like to point out that in this discussion there was also a very technical comment by a developer (Marco Ancona), dated 02/24, in which he explained his difficulties in implementing OAuth combined with EAS on its own calendar app for Android.

Hello, been reading this thread daily. Those using M365/EAS, there is a supposed fixed resolution here 29 Feb. https://support.microsoft.com/en-us/office/outlook-desktop-exchange-activesync-connections-stopped-working-in-version-2401-da2dc0dd-297e-48ba-b6d9-ab18f5d522fc My hotmail (Microsoft email, outlook etc.) account has also been affected since (HST) 24 January on my Kindle Fire.  As a side note about 1-2 times a year for about 5+ years, email would get the authentication error that would last 2-3 days. Web outlook would be fine so confirmed never a password issue. My tablet is older, Fire HD 10, 7th gen, Fire OS 5.7.1.0 (8/23/2023) but works (99% of the time-got the authentication error twice, possibly more times since using spouse's tablet so may not have seen it, but error cleared on its own within couple minutes or follow prompt to enter via web my hotmail password) on a newer tablet Fire HD 10 Plus, 11th gen, Fire OS 7.3.2.9 (2/12/24). Will have to buy a computer because of this. I think there is more to this issue, since many have intermittent successful connections even if for short periods. Hope all those active on this thread will continue to comment, to get better definitive answers, because they should be able to specifically identify what actions led to the timing of this event.

As a side note about 1-2 times a year for about 5+ years, email would get the authentication error that would last 2-3 days. Web outlook would be fine so confirmed never a password issue.

I concur! I have the exact same experience!! It pops up on my desktop Outlook but more frequent on my Android device via its Exchange accounts setup. And as exactly as you said, it last a few hours or sporadically up to a couple of days and it would go away. I suspect because the issue went away in a short amount of time, nobody bothered to create a big thread to discuss it or it didn't get the visibility like this time.

For what it's worth, my desktop Outlook 2013 has been a lot better in the last 3-4 days. I get one-pop a day at the start of my day, like an overnight time-out with the authentication. I can simply cancel the pop and I am good for the entire day. My phone, however, experience more of the pops, but it does recover on its own, whereas over last weekend, it was out the entire few days.

As a few others mentioned, sync of email/contact/calendar are extremely important for most people in today's world and if MS does not find a way address this issue, then it's going to cause people to move away to other platforms. The key issue here is that at Outlook for Android app's sync'ed data is stored locally within the app or its cache, and it doesn't seem to be stored in the device-wide email/contact/calendar storage. Android or iOS's native Exchange support do that and store those in the device-wide storage. The benefit of that is other applications can access these device-wide storage, so you can for example access your contact list from a VoIP/chat app without having that app login into your MS or Google accounts.