Not receiving emails

I noticed that I am not receving any emails to my att.net account. I tried calling customer service and found that to be very un-helpful. I tried sending an email to the att.net account from my gmail account and it was sent without any issues. I then went to check my att.net account and saw that it was never received. I also had a hacking issue a few days ago and I am wondering if that contributed to the issue. Can someone please offer any help? I would really appreciate it. It's curcial that I am receving emails to my att.net account.