The Yahoo mailing list server is notoriously unreliable
and randomly drops mails and/or drops people from lists because their email
server was temporarily refusing mails (4xx SMTP responses not 5xx). I also find
the Yahoo groups web interface absolutely awful; mailman's list archives
aren't great, but are ok for casual browsing, and you can download the entire
archives and load them up locally if you need to.
A quick look around Google groups suggests that my
initial assumption that it'd be as bad as Yahoo groups is probably
unfounded. But if I hadn't already given in and created a Google account
for other things, I'd be unhappy about doing so just for your list, given the
way it tracks your web browsing in ways that I don't entirely understand while
you are logged into it.
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