[Mimedefang] Virus scanner tempfail can cause RFC2821 violation

[David F. Skoll]

On Wed, 12 Mar 2003, Mark Suter wrote:

> A problem with a virus scanner after the DATA command has been
> issued causes a violation of RFC2821, section 4.1.1.4:

>     ... If the processing is successful, the receiver MUST send
>     an OK reply.  If the processing fails the receiver MUST send
>     a failure reply.  The SMTP model does not allow for partial
>     failures at this point: either the message is accepted by the
>     server for delivery and a positive response is returned or it
>     is not accepted and a failure reply is returned.

A temporary failure indication is allowed by the RFC; read it
carefully.

What the RFC says is you can't allow for *PARTIAL* failures.  That is,
you can't allow for success for some recipients, and failures for others.

A temporary failure response code is specifically allowed at the
end of the data phase; see Section 4.3.2:

DATA
      I: 354 -> data -> S: 250
                        E: 552, 554, 451, 452
      E: 451, 554, 503

The RFC specifically allows for 451 or 452 return codes after the
data phase.

--
David.