The effects of smtp blacklists on server bandwidth

The effects of smtp blacklists on my low bandwidth server

I have been using blacklists longer than this, but not on all my MX hosts, which is very often forgotten or practical (e.g. many companies use a backup queue offered by their ISP.)

If you don’t have blacklists enforced on all your MX, don’t bother doing them at all, as spammers will get passed them through your other MX hosts.