Have to Reset Password Every Time I Sign Into ATT.net Email Account

For months now, I have to reset my password every time I try to sign into my att.net account.  I have home internet, home phone, and cell phones through AT&T, and it doesn't help me get into my email account.  Most of my mail is sent to a separate account now but I still need to use this one at times.  I've searched for answers and found none that worked.  Why is accessing my email so difficult?