Talk:SMTP Status Codes

From ASSPSMTP

Contradictory Error Messages

<server.sendingdomain.tld1 #4.2.12 smtp;550 4.2.13 mailbox temporarily disabled: recipient@receivingdomain.tld4>

This Wiki article condones contradictory error codes. You don't have your SMTP server give out a 550 permanent error and then extend the code with 4.2.13 temporary mailbox failure. This is contradictory. It's either a permanent failure or a temporary failure. It cannot be both. If you want the bounce to be a permanent failure, then it should be 550 followed with 5.2.13. Or, alternatively, it should be error 420 followed by 4.2.13. You should never mix 5xx and 4.x.x codes because a proper bouncing handling system won't know what to do with this bounce (i.e., is it a temporary failure or a permanent failure).

If you want to ensure that people handle your bounces correctly, you need to error code them correctly. This Wiki article is just endorsing bad system administration practices. I didn't alter this article because I felt that discussion was warranted first in case someone else has a valid argument for this contradictory usage.

• The example DSN in this article is in-fact a real DSN that I have received many times. The 550 and 4.2.1 codes are actually mutually exclusive of each other, so they do not contradict. The codes individually reflect the possibility of different interpretations of the error between older or newer MTAs. An older MTA would not understand the 4.2.1 (not being aware of the Extended SMTP specification), so a 550 must also a part of the message so that MTA knows the message was rejected. I understand your point, and for the purpose of an example perhaps a less confusing example should be used - but it does exemplify how these codes can be confusing. I will try to make this point clearer in the opening paragraphs of the article. --ME2 07:18, 1 November 2007 (PDT)