Re: Delivery Status Notifications - What is required from the remote MTA?

Wietse Venema

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Nov 30, 2011, 6:50:16 PM11/30/11

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Russell Jones:
> <html>
> <head>
> <meta content="text/html; charset=ISO-8859-1"
> http-equiv="Content-Type">
> </head>
> <body bgcolor="#FFFFFF" text="#000000">
> Nevermind, I have finally found an article that explains DSN from
> behind the scenes. It is quite different than just a standard "250
> OK" status message of course. Article was written in 1997
> apparently, but still helpful
> (<a class="moz-txt-link-freetext" href="http://email.about.com/library/weekly/aa082597.htm">http://email.about.com/library/weekly/aa082597.htm</a>)<br>
> <br>
> On to a different question, does Postfix have any features I am
> unaware of that can still generate a "success" message if the remote
> mail server responds with a "250"?<br>

Postfix will send DSN "success" notification when the remote server
does NOT announce DSN support.

If the server announces DSN support, then Postfix is no longer
responsible for sending DSN "success" notification.

Wietse

Russell Jones

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Nov 30, 2011, 6:53:00 PM11/30/11

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Hi Wietse,

Thanks! That's different from what I read in that article then...
according to that article the remote mail server needs to support DSN as
well for the reports to be generated.

If what you are saying is correct, how can I go about diagnosing why I
am not receiving DSN "success" notices when mail is sent to this one
specific mail server I provided in my log output?

Russell

Wietse Venema

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Nov 30, 2011, 7:00:26 PM11/30/11

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Russell Jones:

> Hi Wietse,
>
> Thanks! That's different from what I read in that article then...
> according to that article the remote mail server needs to support DSN as
> well for the reports to be generated.

Per RFC 3461..3464, Postfix sends DSN "relayed" (not success) if
the remote server does not announce DSN support. The RFCs are
public documents, so you don't have to take my word for it.

If the remote server announces DSN support, and you receive no
"success" or "relayed" notification, then some remote system does
not implement DSN correctly.

Debugging remote SMTP servers is outside the scope of Postfix
support.

Wietse

Russell Jones

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Nov 30, 2011, 7:12:50 PM11/30/11

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Ah that makes sense!

This problematic mail server does announce DSN when you telnet to it,
while Google, Yahoo etc do not announce DSN support.

Thanks for your help. Final question (hopefully), is there a way to
ignore DSN announcements from remote servers and just treat them as if
they don't support DSN, that way I can get the relay/success emails I
need? I've read through the DSN readme
(http://www.postfix.org/DSN_README.html) and it doesn't appear to cover
that (if it's an option). I also searched for "dsn" on
(http://www.postfix.org/postconf.5.html) for main.cf options for doing
this with no luck.

Wietse Venema

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Nov 30, 2011, 7:33:28 PM11/30/11

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Russell Jones:

> Ah that makes sense!
>
> This problematic mail server does announce DSN when you telnet to it,
> while Google, Yahoo etc do not announce DSN support.
>
> Thanks for your help. Final question (hopefully), is there a way to
> ignore DSN announcements from remote servers and just treat them as if
> they don't support DSN, that way I can get the relay/success emails I
> need? I've read through the DSN readme
> (http://www.postfix.org/DSN_README.html) and it doesn't appear to cover
> that (if it's an option). I also searched for "dsn" on
> (http://www.postfix.org/postconf.5.html) for main.cf options for doing
> this with no luck.

http://www.postfix.org/postconf.5.html#smtp_discard_ehlo_keyword_address_maps

(that's smtp, not smtpd).

Or, more radically,
http://www.postfix.org/postconf.5.html#smtp_discard_ehlo_keywords

Wietse

Russell Jones

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Nov 30, 2011, 7:34:49 PM11/30/11

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Thanks! Just got it working as intended =)

Nov 30 18:33:04 bigbertha postfix/smtp[22632]: discarding EHLO keywords: DSN