One thing I've noticed that may be an anti-spam measure: STN, the ISP that servers Marriott hotels (among others) seems to have a "transparent" proxy intercepting outbound traffic to port 25. Not sure why they'd do that except to deter check-in spammers. They *don't* do anything with traffic to port 80, as best I can tell.
--Steve Bellovin, http://www.research.att.com/~smb (me)
http://www.wilyhacker.com ("Firewalls" book)
