[Mimedefang] OT: Blocking because of MX to 127.0.0.1

[Kevin A. McGrail]

Instead, point the secondary MX to another IP you own, but which is either
unused or which doesn't have an SMTP server running.  Spammers will get a
RESET
packet and give up, while ISPs will get a RESET, queue the mail, and try the
primary MX when it is available again.  Alternatively, it may be worth
trying
the private address ranges, 10.0.0.0/8, 172.16.0.0/12, and 192.168.0.0/16 as
per
RFC1918, especially the 192.168 range, as ISPs are highly unlikely to use
private addresses, or if they do, will use the Class A address for
scalability.
These are likely to be unrouteable, so will fail without even the single
packet
exchange which my scheme uses.



NOTE: We have seen issues with this (and greylisting) especially with
Allegiance Telecom causing 12 to 24 hour queue retries on emails where the
initial connection (or MX record) fails.

Regards,
KAM