On Wed, Sep 17, 2014 at 1:43 AM, Sven Krohlas <sven.kroh...@1und1.de> wrote:
> RFC 7372 proposes to use a 550 response code for reverse DNS auth
> failures, see section 3.3.
>
> Reverse DNS checks are usually done early in the connection (like IP
> blocks) in the connection establishment stage of the SMTP dialog.
>
> RFC 5321 allows only a 554 error response there, see section 4.3.2.
>
> So, shouldn't a 554 code be used here? Or does RFC 5321 need an update?
>
The definitions in 5321 are:
550 Requested action not taken: mailbox unavailable (e.g., mailbox
not found, no access, or command rejected for policy reasons)
554 Transaction failed (Or, in the case of a connection-opening
response, "No SMTP service here")
550 seems right to me. It's a rejection for policy reasons, not a general
transaction failure or the total absence of SMTP service.
-MSK
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