Old e-mail address is showing up on new g-mail account!

I had an e-mail account with MyDomain.com, I terminated my account with them and set up a g mail account a over a year ago, just found out that when people receive e-mail from me the reply is to the old my domain address? I deleted the new g-mail and opened it again, still the same thing ! What am I doing wrong!  What can I do to correct this!