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Re: what to say on timeout?

2004-01-05 12:40:57

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. But a server which times-out a connection is not shutting down -- it is still operating and open for business. So for such a server to send a 421 is a little bit of a lie, and may be misinterpreted by a client.

...   This is about idle timeouts (long inactivity) right?

Yes. This is about when a server is sitting and waiting for the next command from the client, for some number of minutes (This could be a denial of service attack). And it is also about too slow transmission of data after the DATA command. If for instance the client sends only one packet every two minutes, and each packet contains only one additional byte of data, that could be cause for the server to timeout after some amount of time (A denial of service attack could also take this form).

What I am saying if you are going to hang up due to long activity, the only
thing that is useful is the response text.   The code itself is meaningless
since the SMTP client would not know what to do with it.

Thank you for what you imply, but do not say directly, here. You imply that the RFC does not tell what the server should say in this case. You also imply that there is no standard or common practice for what the server should say in this case, because otherwise the client would know what to do.

Can you say -- forthrightly with confidence -- what you imply? that there is no formalized or standard message for the SMTP server to send just before it exercises its option to timeout because of long inactivity or too slow data transmission?

Thank you,

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