Recently I am getting SPAM "bomb" into my inbox which is leaving about 300+ SPAM messages. I checked the SPAM filter and it is on. It appears my email account has been comprimised and is being used for phishing. I called Comcast customer support and they were not able to troubleshoot over the phone but escalated to another team for call back. I received a suspicious call from a third party who attempted to remote into my PC. When I asked him what the issue was he could not tell me. So, in the end I checked the forums and changed my email account password. I also went to web mail and some of it is being catched, but not all. Now, I am unable to send photos from my iPhone to my email address. It appears they are filtering these as well.
Check your Sent folder to see if anything is in there that you know you didn't send. If there is, then the account has been compromised. In that case you need to change the password to something a lot stronger than whatever it is right now, and also change the secret question and answer for the account.
If the Sent folder looks OK, then the most likely thing is that your account is being "spoofed". Spammers can make it look like emails came from you when in fact they did not. If that is the case, there is nothing you can do except notify your contacts of the problem and wait it out. Once a spammer has your email address there is nothing you can do to stop it. But in order to avoid detection they will usually only use an address for a few days or a week and move on to annoy someone else.
Also, use your A/V software to run a complete scan of your machine to see if it can find anything wrong.
Three weeks later and I am still getting SPAM'd. Nothing being sent from the Sent folder that looks malicoius. I was informed Comcast has upgraded their email servers and this may be causing the problem since their SPAM filters may not be in place. Most of the SPAM looks foreign so I am not sure why the email server SPAM filtering is not working. May just close my mailbox and go with Google mail. Customer support has not been any help at all.