- Well, I have a very clever spammer on my hands. I have my Thunderbird filters set to delete anything that's NOT from someone in my addressbook, as well as filters for Yahoo Group emails & other messages. But a spam email still slipped through. Until now, my filters were fool proof & not one spam appeared in my inbox. And now this happens. I looked in the header info & I didn't see anything that was similar to my filters. However, the "from" field has no address. Could this be the reason? Any ideas on how I can adjust my filters so that this doesn't happen again?