This is good to know. I know Comcast is aggressively blacklisting accounts in which all e-mail from a domain name is forwarded to the user's Comcast account. As recommended throughout these forums, I've set my default address to :fail: instead of forwarding as a catchall (bummer, but ultimately no big deal). I'm also keeping track of my good and disposable e-mail addresses, and not using obvious ones like webmaster@..., admin@..., etc.
I tried to configure Spam Assassin today but there are some differences in fields between the tutorials/posts and those in SA -- different versions, perhaps? I need to take a fresh look at it another day and ask specific questions.
Thanks all!