I have been using Comcast for 9 years and have had no problem. I have been using email for a lot more years than that. All of a sudden, when I try and send photos and I have tried to send small size photos to see if Comcast has a file limit but nothing gets back. I get a return message in quotes that comcast can't send it. I have tried sending to family that I have not had problems with. If I go to Gmail I have no problem sending the message. I use Windows Live mail because I like format which is more like a "letter form." I am not really fond of using Gmail or Comcast direct. This is what is returned to me:
"Caxxx and Bxx xxxxxxxxxx" <email@example.com> I put the x's in because I do not want any more unsolicited email.
Can you send the photos if you sign into the webmail using only a browser and not WLM? You need to try that as a test. If it works OK with only the browser, go back into WLM and delete the account. Then recreate it again from scratch.
Just to add: Microsoft no longer supports WLM. It's not getting security updates or bug fixes anymore. You might consider moving to Mozilla Thunderbird, which can do pretty much anything WLM can, and it's easy if you're used to WLM.