problems and this list

Wolfgang S. Rupprecht wolfgang.rupprecht+gnus200707 at
Thu Jul 12 15:38:54 CEST 2007

David Ford <david at> writes:
> That wouldn't cause duplicates.
> You got a 550 error which means delivery was not attempted.

I got a 550 because my machine sent them a 550 for their probe-back.
If my machine waited to answer their probe-back they would wait too.
If my timers were set to break the connection after they hung for a
certain amount of time, my machine would think the transaction didn't
happen but the remote machine might well assume it was "good enough"
and deliver the message.

And yes, waiting a while after accepting the SMTP connections is a
common anti-spam trick.  It lets your SMTP see if the other side is a
simple timed shell scripts that doesn't really read the SMTP replies.
Probe-backs also get confused by 450 "graylisting" which will lead to

Feel free to claim that every SMTP server in the rest of the world is
all conspiring against  The bottom line is they have DNS
errors and are using a silly probe-back method that isn't very robust.

Wolfgang S. Rupprecht      
IPv6 on Fedora 7

More information about the community mailing list