The development team has implemented an anti-spam program called Defensio. It identifies posts that contain possible spam, including links and email addresses, and places those posts in a holding location where the moderators can screen them and decide it they are spam or not. The system has some artificial intelligence features and learns as the moderators identify posts as spam or not-spam. It has intercepted quite a bit of spam posts, and has also held non-spam posts for review. Overall, I think it is going pretty well.
We used to ban broad swaths of IP addresses and email addresses from suspected spammer domains. This system is letting people join, but is holding suspicious posts for a manual review. What you suggest seems to be one of the triggers that could get a post by a new member intercepted into the spam reviwe area.