North American Network Operators Group
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Re: Spam filtering bcps [was Re: Open Letter to D-Link about their NTP vandalism]

  • From: Steve Thomas
  • Date: Wed Apr 12 13:18:19 2006 
> I haven't seen any succinct justification for providing a
> 550 message rejection for positively-identified spam versus
> silently dropping the message. Lots of how-to instructions
> but no whys.

RFC 2821?

  ...the protocol requires that a server accept responsibility
  for either delivering a message or properly reporting the
  failure to do so.

  ...

  If an SMTP server has accepted the task of relaying the mail
  and later finds that the destination is incorrect or that
  the mail cannot be delivered for some other reason, then
  it MUST construct an "undeliverable mail" notification message
  and send it to the originator of the undeliverable mail (as
  indicated by the reverse-path).

Unless you're the final recipient of the message, you have no business
deleting it. If you've accept a message, you should either deliver or
bounce it, per RFC requirements.