[Mimedefang] Revisit: Filtering on HELO

David F. Skoll dfs at roaringpenguin.com
Mon Mar 26 08:43:50 EDT 2007

Philip Prindeville wrote:

> That still goes towards my point, which was that the host
> uses the address of the interface that's outbound for the
> connected socket.

Not by default.  By default, sendmail uses whatever
"hostname -f" returns (that's Linux syntax; hostname on other
UNIXes might behave differently.)

> Remember: the original point was that if a host is
> multi-homed {A.A.A.A, B.B.B.B, C.C.C.C}, that it is
> incorrect behavior to say "EHLO [B.B.B.B]" on a
> socket that is bound to any local interface *other
> than* B.B.B.B.

Why is it incorrect?  A multihomed host can call itself any of its
IP addresses.

The only kind of HELO filtering I do on my server is to reject remote
hosts that call themselves "www.roaringpenguin.com" or
[], because I know they're lying.


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