Learn something new every day
For the last day and a half, my messages to the Jetspeed mailing lists have not been delivered. I was starting to be afraid I either had a really weird system problem or I'd been silently blacklisted. I tried sending mail to postmaster@jakarta.apache.org, and received a reply that set me straight. Apparently, since I changed the domain name I use in my e-mail, my incoming messages were from a different address than the one I'd subscribed with. Therefore, my messages were queued for a moderator. The Jetspeed moderator is travelling, so my messages haven't been delivered.
I've corrected my subscription, so hopefully I won't be bothered by this problem again. It was intersting to know though; I'm sure this is how spam is avoided.