email timeing out

I just got Xfinity and started using their email. It times out after 30 or so min. (non-use)
I think it may be in the email client. Or maybe Comodo?
Something is doing it and I have searched the help files with out any success.

Any ideas would be helpful
thanks in advance

Are you using their webmail? It is not uncommon for websites where you are logged in to be logged out after a period of inactivity because of safety considerations.