I need help with this one, if I try to send an email to anyone at
@bigpond.net.au I get these 2 errors below but if I telnet to their
MX hosts port 25 directly then a test message will go through okay
so it seems to only be a problem when I send via my local courier-mta.
Apr 30 16:09:27 mail courieresmtpd: error,
relay=::ffff:xx.240.81.28,msg="502 ESMTP command error",cmd: DATA
It's highly unlike that it's "anyone"@bigpond.net.au, but rather these
specific recipients. Looking earlier in your mail log you should see a
single delivery failure to these addresses, which starts the backscatter
This is backscatter suppression. You can read up on it in INSTALL and the
courier man page.