I extend my gratitude to you for contacting us about this issue through the forums and please, accept my sincere apologies for any inconvenience that you have experienced.
With regard to accessing your new sub-account. You can access it on our Home Page-Webmail. The same workaround in accessing your Primary Email Address is to be followed.
First, you go to our Home Page: www.att.net, then you click on the Mail icon under Personal Assistant. After that you would be asked to log-in using your complete email address and then put in the password and press Sign in. That's it! You should be able to access your emails then. Again, accessing your Sub-account email is just the same as with your Primary email address. By the way you have to log-in and log-out from each email address.
For further assistance, please refer to this helpful link from our Support Site: www.att.com/esupport
Should you need further help regarding your post, please feel free to post your reply on this thread or you may call our Technical Support Helpdesk. You may reach them at 1 888 321 2375 if you are from these states - KY, TN, NC, SC, LA, MS, AL, GA, FL; and 1 877 722 3755 if you are located in CA, NV, KS, MO, OK, AR, TX, WI, MI, IL, IN, OH, CT.