Re:Inaccurate title/summary (Score 1)

My list servers do no such thing. If a list alias doesn't exist, my MTA rejects it w/ a 5xx level SMTP error as it should. My list software would create this type of backscatter if my MTA were misconfigured and accepting email for any left hand side as google's apparently does.

Cute postfix recipe to help w/ backscatter:

main.cf:
smtpd_restriction_classes =
    has_null_sender
has_null_sender =
    reject_rbl_client ips.backscatterer.org
    reject_rbl_client bl.spamcop.net
smtpd_recipient_restrictions = ...
      check_sender_access hash:/etc/postfix/null_sender ...

null_sender:
        has_null_sender