>This seems to be something specific to LISTSERV -- I've never seen it with
 >other lists I've dealt with, or with private email.  The only time anyone
 >thinks I'm relaying something is when I really am doing so (connected from
 >one place, trying to log into an SMTP server somewhere else).

I see alot of stuff via LISTSERV that I don't see otherwise. Why? because as an individual, I'm not in the habit  of sending email 7x24, though LISTSERV generates distributions around the clock, and the bounces (relay blocks) that occur late in the evening due to use of incorrectly configured and less-preferred MX hosts, do not seem to occur during prime-time when the more preferred and better configured hosts (networks) are available (like obi-Ben said).

/Pete