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Re: what to say on timeout?

2004-01-05 13:32:38

On 1/5/2004 1:40 PM, Richard O. Hammer wrote:

Hector Santos wrote:

Send a 421 per RFC 2821 section 3.9.

One problem with 421 is that it normally means something else: I 
believe that 421 normally means that the SMTP server is shutting down 
for some reason.

That's the interpretation that is explicitly endorsed by the text in
RFC2821, but in the general sense, 421 just means "service unavailable",
which can include the (stated) case of critical failure, but can also mean
"oops, i'm out of disk space", or the ultimately generic "i'm bored with
this coversation". The client impact is pretty much the same in all of
these cases -- requeue the message(s) for delivery -- and it doesn't
really matter why. I suppose somebody could make the argument that a
server that is going down is probably going to be down for a while and
that another server could (or even should) be tried, but this isn't stated
anywhere in the algorithms and its not very pure logic, since a service
could just be termporarily recycled, or temp space could be freed, or
whatever, and those kinds of counter-scenarios nuke that argument.

Eric A. Hall                              
Internet Core Protocols

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