Just to follow up, the patched pop3.el seems to be working fine as
as keeping uidls in separate files for each server. However, I
*still* can't get changing the state of pop3-leave-mail-on-server to
work. I use :prescript functions on my mail-sources to set the state
of this variable. If it's set to t, everything works fine. The mail
gets left on the server, and I get it. If I set it to nil in a
prescript, I get no mail from that server (though it is left there.)
Strange. I'm out of ideas at this point.