I wrote:
I don't see how it "spreads the load" or
how the spammer benefits
in any way. The spammer wants to get the spam to as many valid
email addresses as possible, but sending to the backup MX doesn't
get it to more valid email addresses, and it doesn't reduce the
load on the spammer's sending machine.
John wrote:
Were they talking about relaying and authenticating
senders, or
about sending to a user at the MX[n] host?
Talking about spamming software that ignores the MX precedence and
sends to backup MX hosts even though the primary is online. I said
that I wasn't sure if that was deliberate or just sloppy. I can't
see any reason for it to be deliberate, unless it's intentionally
malicious.
Eric