On Thu, 19 Aug 2004, David Woodhouse wrote:
> Doesn't the rejection already give enough information to the
> offending sender, if in fact the message is genuine?
To their MTA, certainly. But then what...?
> 550-Callback setup failed while verifying <gxsr@???>
> 550-Called: 202.108.45.232
> 550-Sent: MAIL FROM:<>
> 550-Response: 553 You are not authorized to send mail as <>
> 550-The initial connection, or a HELO or MAIL FROM:<> command was
> 550-rejected. Refusing MAIL FROM:<> does not help fight spam, disregards
> 550-RFC requirements, and stops you from receiving standard bounce
> 550-messages. This host does not accept mail from domains whose servers
> 550-refuse bounces.
> 550 Sender verify failed
I gather that the users of certain commercial MTA software, if they're
lucky, will get that reported to them as "Sender verify failed".
If they're less lucky, they'll get told:
Status: 5.1.1 (bad destination mailbox address)
Remote-MTA: dns; othello.physics.gla.ac.uk
when in fact we told them:
550 Fraudulent sender address detected:
(taken from an actual incident yesterday).
