AT&T Mail on Outlook 365 stopped working

I just performed a tech support call with someone experiencing the same issue. It appears that AT&T has changed their security configuration (again) which is why you are no longer receiving mail. I was able to to get my client's email working by doing two things. The first is to check your email account setting in Outlook and check the "Require logon using Secure Password Authentication" box.

The second thing I did was to create an app password or as AT&T refers to it a "secure mail key". You can do this by logging in to your account, go to your profile and then select secure mail key. The app password is meant to be a security mechanism where each app gets it's own unique password to connect.

https://www.att.com/support/article/email-support/KM1240308

Unfortunately this was a process of trial and error that took about 2 hours to discover. I could not find any documentation about this and as usual calling their tech support was mostly talking to a computer assistant that didn't understand what we wanted. There's no way a normal person would have figured this out without help.

After spending hours on this issue today, I found this article on AT&T site. My mail is now up and running. 
https://www.att.com/support/article/email-support/KM1086159/

None of that above works. Last week, my att.net suddenly stopped working in outlook-office 16 with win 8 on one computer and in outlook-office 365 with win 10 on another computer. It also stopped working in outlook on my win 10 phone. It does, however, still work in my outlook on my android phone.  I have not been able to find any solution. Right now, I can only get my att.net email by going to att.net to get it. I have numerous email addresses and they all come into my outlook box. I am not going to continue to go elsewhere to get the email from just one account. I will simply delete that account. Perhaps att.net does not want to support email anymore.

We can help you get back into your email, @maz! 

The best way to test your att.net email login is on www.currently.com. 

If you can't get to that page because it redirects to another AT&T page, clear your browser history. You can start on partial history if you prefer but it may need to be "All Time" history. 

If you can get to currently.com but you can't get logged in, there is a "forgot password" option or you can change your password on our Email Password Reset page. If you have other AT&T services and your att.com user ID is your email, when you reset your email password, it will reset both. 

Once you are able to log into your webmail, we can work on your clients such as Outlook. We recommend clients that are compatible with OAuth.

If your client is not compatible you can use the secure mail key with compatible versions of other clients. Secure mail key instructions and compatible versions are listed under the OAuth instructions on the link above.  

If you have any other questions or issues, please let us know!

Raychel, AT&T Community Specialist

I had the same problem of trying to get my assigned ATT email to work with Outlook 365. Finally got it working by using a Created secure mail key and using it as my password. Both boxes were checked: [ ] This server requires an encrypted connection (SSL/TLS) and [ ] Require logon using Secure Password Authentication (SPA). Server used was: pop.mail.yahoo.com / 995   Here is a link to creating a secure mail key if you haven't already done so. Hope this is helpful. https://www.att.com/support/article/email-support/KM1240308

I too, quit receiving or being able to send emails from my default ATT email account when using Office 365 Outlook. Got it working after many attempts by substituting my email password with a created Secure Mail Key. Both boxes were checked: This server requires an encrypted connection (SSL/TLS) and Require logon using Secure Password Authentication (SPA). Used pop.mail.yahoo.com as my server and Port 995.  Hope this is helpful to someone, since it is confusing and time consuming to figure out. Website for creating a secure mail key: https://www.att.com/support/article/email-support/KM1240308

Hope this is helpful...........

Use myAt&T app on your phone

On myAt&T App:
Click on More at bottom right corner

Then:  Profile - Sign-ing info - Secure mail key

And get the new secure mail key

It's a long set of letters so -
Remember to copy/paste or write it down

Go to your Outlook and Add or edit account manually,  and select POP setting
If asked, enter your regular password

Incoming mail Server:
pop.mail.yahoo.com
Port: 995

Check:  This server requires an encrypted connection (SSL/TLS)

Check:  Require login using Secure password
Authentication (SPA)

Outgoing mail Server:
smtp.mail.yahoo.com
Port: 465

Encryption method:  SSL/TLS

Check:  Require login using secure password authentication (SPA)

On the next screen, for password
Enter your secure mail key

That should do it!

If I need to add a second ATT account to Outlook?  I can't go into My att app & request a second secure mail key & the one that I got for the first account won't work.  It's driving me crazy because I have important saved emails that I can't access.  I hope you have an idea.  I spent 25 minutes on the phone with ATT only to be told they don't support personal emails.

Yes, it has been a pain dealing with this Yahoo/ATT email change. I had to use the ATT/Yahoo webmail until i could get it working - maybe you can access your saved emails there, hopefully. Can't figure out why you couldn't ever get the first secure email key to work? All of the settings for setting up the account should be in my previous comment and Blake7's post. You must use the security key as your password! I included a link in my previous post for the site to get a secure mail key. 

https://www.att.com/support/article/email-support/KM1240308

First try logging into yahoo/att webmail and see if your old password still works - it does not use a secure key for it only Microsoft. Also make sure you are able to login to your Microsoft account. 

Att email has always been a hassle for my clients.  I have always tried to get them to either accept the fact that they can only get their emails from the ATT.net website...or start migrating to a more "standard" email, such as with Microsoft or gmail.  This should not be so hard.  Trying to get it to work with Outlook365 is futile.