Access your AT&T Mail using your favorite email apps
   Synchronize other account info, such as your calendar and contacts, to your email app.

   Go to your myAT&T Profile. Sign in, if asked.
   Scroll to My linked accounts, select the email account that needs a secure mail key.
   Scroll to Secure mail key, select Manage secure mail key.
   Choose the email address that you’d like to use, if you have more than one.
   Select Add secure mail key. Enter a nickname for the secure mail key to make it easy to recognize.
   Choose Create secure mail key.
   Select Copy secure mail key to clipboard. Make a note of your secure mail key for further updates.
       For security purposes, the secure mail key only displays until you select OK.
       If you lose or forget the secure mail key, you can always create new secure mail keys.
   Select OK.
   Go to your preferred email app, replace the existing password with your secure mail key. For an IMAP account, delete the existing password for both the IMAP and SMTP servers. Replace them with your secure mail key.

I am guessing that my inbox messages disappearing had something to do with a Thunderbird update. Pay attention mainly to the lines that mention "key". Access your AT&T Mail using your favorite email apps Synchronize other account info, such as your calendar and contacts, to your email app. Create a secure mail key It’s easy to create a secure mail key from your mobile device, tablet, or computer. Have your User ID and password ready to sign in to myAT&T. Go to your myAT&T Profile. Sign in, if asked. Scroll to My linked accounts, select the email account that needs a secure mail key. Scroll to Secure mail key, select Manage secure mail key. Choose the email address that you’d like to use, if you have more than one. Select Add secure mail key. Enter a nickname for the secure mail key to make it easy to recognize. Choose Create secure mail key. Select Copy secure mail key to clipboard. Make a note of your secure mail key for further updates. For security purposes, the secure mail key only displays until you select OK. If you lose or forget the secure mail key, you can always create new secure mail keys. Select OK. Go to your preferred email app, replace the existing password with your secure mail key. For an IMAP account, delete the existing password for both the IMAP and SMTP servers. Replace them with your secure mail key. Good to know: Each device you use to access your email will have its own secure mail key. Additional secure mail key notes Access your AT&T email account without an OAuth mail app or secure mail key You can always read and manage your email through a Web browser at currently.com. A secure mail key won’t affect your AT&T email password You’ll still use the same password for your AT&T Mail account in OAuth-compatible apps, myAT&T, and other AT&T products like currently.com and webmail. When you change your AT&T email password, you won’t need to get a new secure mail key. Keep your secure mail key as long as you like Secure mail keys never expire. Create a new secure mail key for a blocked or locked account For safety reasons, we delete secure mail keys whenever we have to lock or block your account. If that happens, you’ll have to create a new secure mail key for each AT&T Mail account. Give your secure mail key a nickname Create a nickname to identify your secure mail key, especially if you have more than one. It’s much easier to recognize a nickname, like Ari’s email or Kelly’s email, than the 16 random characters you entered when setting up your email. Last updated: March 12, 2025 When I went through this process, it showed a key from 2024. I merely deleted it and from the same page created a new key. After that 500 emails from the last week started downloaded to my inbox. Happy again. Bill