Comcast denies my messages to Mom

It has happened again. Comcast suddenly started blocking all of my e-mails to my mother who has a Comcast e-mail address. This has happened once before and they were pretty quick about removing the block, but it is discouraging that I am having to deal with this again. How many more times will they block it in the future? Comcast's FAQ about this issue says:

Our filters have determined that email from your mail server has been sent in patterns which are characteristic of spam.

I am positive there isn't any spam coming from my Mac, but that really isn't the issue here. The actual blocked IP address is the server which hosts iwankerl.com and I don't really have much control over that (aside from finding another hosting company). The IP address is shared with other domain names so I suspect that maybe some other customer of phpwebhosting.com is the one sending spam and causing me grief.