Hi Rolf,
At 01:56 16-04-10, Sonneveld, Rolf wrote:
The real problem here is that mail software from a recipient, that
validates the headers of a message, might reject the message, which
means a double-bounce (as we're talking here about invalid headers
of notification messages causing a reject). For instance the mail
adapter in SAP is such an SMTP server implementation which reject
these type of messages at the end of the DATA phase, after the
single dot. And we can't really blame SAP for this, after all why do
we have standards?
The rejection at the end of the DATA phase won't cause the SMTP
server to generate a bounce. The DSN is generated by the SMTP
sender. There are two possible problems. I'll use Section 6.4 of
RFC 5321 for the easier one which is invalid headers:
'Unfortunately, variations, creative interpretations, and outright
violations of Internet mail protocols do occur'
'The debate as to whether a well- behaved SMTP receiver or relay
should reject a malformed message, attempt to pass it on unchanged,
or attempt to repair it to increase the odds of successful delivery
(or subsequent reply) began almost with the dawn of structured
network mail and shows no signs of abating. Advocates of rejection
claim that attempted repairs are rarely completely adequate and that
rejection of bad messages is the only way to get the offending
software repaired. Advocates of "repair" or "deliver no matter what"
argue that users prefer that mail go through it if at all possible
and that there are significant market pressures in that direction.'
The second possibility is discussed in RFC 3464.
Regards,
-sm