3rd Party Email Servers Not Able to Login - Yahoo repeatedly making me login when on the web

Thank you for that information, @DKon!

If you are setting up the email manually, as in inputting the settings yourself, you will need to create a secure mail key. If not, you will experience errors. 

You can create a secure mail key using these steps:

1. Go to Profile and choose Sign-in info.
2. Select the email account that needs a secure mail key. (You’ll find a menu at the top if you have multiple accounts.) 
3. Scroll to Secure mail key and select Manage secure mail key.
4. Choose the email address that you’d like to use, if you have more than one.
5. Select Add secure mail key and then enter a nickname for the secure mail key to make it easier to recognize.
6. Choose Create secure mail key.
7. Select Copy secure mail key to clipboard. Make a note of your secure mail key, so you have it handy if you need to update an email app on several devices.
   • For security purposes, the secure mail key only displays until you select OK. 
   • If you lose or forget the secure mail key, you can create new secure mail keys.
8. Select OK.
9. Go to your preferred email app and replace the existing password with your secure mail key. For an IMAP account, delete the existing password for both the IMAP and SMTP servers and replace them with your secure mail key.

We look forward to hearing if this helps!

CalebP, AT&T Community Specialist 

You're running into multiple issues.  At the current time Windows Mail is broken when it comes to working with Yahoo-based accounts like AT&T.  Not only won't it download all of the mail, some emails don't display properly, like the raw HTML code is showing.  It appears Microsoft broke it with an update early in June. 

Outlook and other email clients can't use the same password that works when you use a browser to log into your account online.  They need a Secure Mail Key  that is used wherever a password is called for. 

Thunderbird, if using current versions, should be set to use OAuth2 for authentication, not Normal Password (or SMK).  When you do this you should be taken to the login portal where you put in your email and normal password one time.

Oops, forgot one more issue (there are SO many right now)....

Some of the email server certificates are messed up.  If you don't have success using the "correct" imap server names (imap.mail.att.net and smtp.mail.att.net) then try imap.mail.yahoo.com and smtp.mail.yahoo.com.

We'll do our best to help you with your email, DKon.

Troubleshoot your mail client with our Login and Email Solutions article. Use the section titled 3rd Party Mailbox - (Outlook, Apple Mail, Mozilla Thunderbird).

• Test using webmail - If you are able to sign in to your email via the web, the issue points to the app or mailbox you are using.

• Mailboxes - We recommend using the latest version. Updates and changes may prevent it from working properly. 

• Rebuild your mailbox profile - In some instances, rebuilding the profile fixes some issues. You may lose email doing this.

• Change your settings from POP to IMAP.

Please keep in mind that AT&T does not officially support or troubleshoot mailboxes/clients like Outlook.

Let us know if this helped or if you need further assistance.

Aminah, AT&T Community Specialist

I've run through all the possible solutions. I deleted my email from Outlook months ago and it still won't reinstall today. I also tried Thunderbird for the first time today but it never gets past the Checking Your Password stage. At this time, Mail is the only app that is working with my email but it is downloading only a few of them a day and often several minutes later than they arrive in my Yahoo mailbox that I am viewing through the web. With multiple email service providers having issues with my Yahoo mail, I believe the issue is with Yahoo and not the third-parties. As I previously said, this all began some time ago when I was performing a mailmerge to about 100 recipients. Is it possible my account was limited in some way at that time because it was flagged as a possible spammer?

Thank you. It was very useful to know why Mail is behaving badly.

I've tried in the past to set up Outlook with my Secure Mail Key and it failed again today, but I was able to set up Thunderbird with it. I was able to do that with the autodetect authentication and using POP.

Hopefully I can make this work for me. I haven't used Thunderbird in years.

Look in the Account Settings and see if Thunderbird end up with Authentication method showing OAuth2 for that account. It should have if you let it do autodetect.

If so, that might explain why Outlook would fail.  Some have had to delete their SMK and create a new one, for reasons unknown.  If Thunderbird automatically went with OAuth2 you wouldn't know the SMK was bad.

Checking the settings on Thunderbird it says it's using a Normal Password, but used the SMK to setup. I'll have to admit defeat on Outlook for now. Nothing seems able to connect. I'm sure I'll end up having to delete it and reinstall.  Thank you both for your help.

Thank you for the update, @DKon.

As @Tonydi mentioned, try creating a new secure mail key and use the new key to log in. This has helped resolve issues in the past, especially when signing into another email client. 

Let us know if this helps get you logged into outlook.

Elmi, AT&T Community Specialist.