we used to run an "open relay". we had measures in place to keep it
from being used by spammers, and they worked. but it would pass the
blacklisters' tests for open relays, so we got blacklisted. and
people started to refuse mail from us.
Could you elaborate a bit about the measures you used to prevent is
use by spammers?
we counted the number of non-local recipients of mail sent through our
relay from non-local, unauthenticated users. we would only allow a few
recipients (I think the number was 15) from any one IP address per day.
this was sufficient for our mobile users, who sent only a few messages
per session, most of which were to local recipients. but it was a small
enough number to discourage spammers from using us as a relay. a couple
of them tried it, but gave up when only a few messages got out.
actually we were pleased that they wasted their time trying to use our
relay :)
I'm not sure why open relays are useful now... don't all networks/ISPs
have local SMTP servers these days?
it's a pain in the wazoo to have to change your SMTP server every time
you connect to a different network.
authenticated submission is a better fix. but it's still not widely
used.
Keith
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