Really disappointed in AT&T internet - not helpful and heck-bent on extorting $ out of customers

The "reply to" field is corrupted somehow and my helpers didn't bother to explain whether that is fixable.

Did you bother to look at your webmail settings?  Click the settings gear -> more settings -> mailboxes -> click on your account and in the pane on the right is that account's specific settings.  What does Reply-to address say?  If it's wrong fix it.  Clicking the little downward pointing triangle on the right end of the Reply-to address field shows you other choices if there are any others besides just your account.  Including your actual account additional choices come from the Send-only email addresses and Disposable email addresses.  Send only and disposables appear in the Mailbox Management pane (middle pane).  After you selected the desired reply-to click the Save button at the bottom.

if the send-only's and disposables have suspicious entries delete them.  And if you didn't create them then you were indeed "hacked" since the only way those can be created was for someone to actually get into your account.  Given that's the case below is my standard list of stuff you should check and possibly fix:

• Change your password and security questions. The link I supplied allows you to change the password three ways; using your security questions, using your recovery email address, or by snail mail.
• Log into your webmail through start.att.net and click the settings gear->more settings. In there you will see a number of commands on the left. The ones that need checking are Mailboxes, Filters, and Security and Privacy.
• Mailboxes. Click that and choose an account in the Mailbox list to bring up that account's settings panel on the right. Check the name and reply-to address and see if it is suspicious. Blank it out if you don't want that set. Check the forwarding setting and make sure it is blank or what you want. Check the other settings there as well. When you are done click the Save button at the bottom to update that account's settings. (name and reply-to already discussed earlier)
• Filters. Look for suspicious filters and subtle filter names like '.' (a dot) or ':'. Remove them and click the Save button.
• Security and privacy. Make sure no addresses are defined who's email you don't want blocked. Click Save to update those settings.
• Contacts list.  While it doesn't affect the running of the webmail it's still good to check to see if everything you expect is there.  If you contacts are gone you may be able to restore them clicking on the Contacts Actions in the toolbar and selecting "Restore from backup...".

This thread addresses Customer Service, or the complete lack thereof. I needed some help fixing email, and AT&T tried their best to completely screw me over. I talked with one completely useless person who could barely speak English and one seemingly competent person who could also barely speak English: their communication skills were abysmal. In the end the competent man had absolutely no interest in helping me: he had his shallow marketing script and basically tried to shake me down for $180 for something he could have solved in 60 seconds. I solved the problem on my own, no thanks to AT&T. Companies like AT&T that give a {edited for word filter evasion} to its customers are so disappointing.