ietf-smtp
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Re: slow email validation problems (was reject vs bounce)

2005-09-15 08:58:15

On Wed, 14 Sep 2005, Paul Smith wrote:

RFC 2821 bis should also (IMHO) recommend (rather than just "suggest") the
behaviour described at the end of section 4.2.1:
"In many cases the SMTP client then simply needs to search for a line
beginning with the reply code followed by <SP> or <CRLF> and ignore all
preceding lines."

It should also say (IMHO) that the reply codes on the preceding lines should
be deemed to have been overridden by the final reply code in case they are
different ( unless the specification of the particular command being replied
to says otherwise).

That's a very bad idea for a number of reasons.

(1) There is code out there which takes the response code from the first
line, not the last.

(2) Servers often provide multil;ine responses with important information
in the text on all lines, e.g. to explain a 550 rejection.

(3) The assumption up to now has been that reply codes must be consistent;
this is not something that you can change at such a late stage.

(4) If you want to change SMTP or add features, write a service extension.

IMO the informal suggestion in the last paragraph of 4.2.1 should be
removed. It was originally from a non-normative appendix in 821, and
probably should not have been promoted to the body of the specification
without closer scrutiny.

Tony.
-- 
f.a.n.finch  <dot(_at_)dotat(_dot_)at>  http://dotat.at/
BISCAY: WEST 5 OR 6 BECOMING VARIABLE 3 OR 4. SHOWERS AT FIRST. MODERATE OR
GOOD.