[Mimedefang] MX resolves to localhost

[David F. Skoll]

On Mon, 16 Aug 2004 Matthew.van.Eerde at hbinc.com wrote:

> The theory goes that if bad.example.com goes to 127.0.0.1, then your
> test of RCPT TO: joe at bad.example.com will be against localhost - and
> localhost should certainly deny this as it would be an open relay
> otherwise.

The theory is good, but the practice is bad.  If you connect on the
loopback address, 99.99% of Sendmail installations will permit relaying.
The remaining 0.01% are broken. :-)

Regards,

David.