Email Not being sent to recipients from the xfinity connect site from my home computers

Recently like a week or so ago. It was reported to me that my emails were not being recieved. Although they show as being sent from my end. I did some testing and when I send from one comcast.net account to another..they show up but in the spam folder only. It sounds like maybe my IP address is being flagged as spam? and not actually sending? Please advise