Response codes
in [Postfix]
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From: "Mark Scholten" on 30 Apr 2010 14:07 Hello, Should a system that gives the following response to a SMTP request give a code 450 error or a code 550 error (I did think a code 550 should be given). (host mxfilter4.domain.net[70.34.y.z] said: 450 4.1.1 <user(a)domein.nl>: Recipient address rejected: undeliverable address: host mail.domein.nl[70.34.x.y] said: 550 "Unknown User" (in reply to RCPT TO command) (in reply to RCPT TO command)) I did change domain names and the email address and IP addresses (as they aren't needed in this example and pointing to someone is also something I don't want to do). Is what I suspect correct or are I wrong? Current situation: - it gives a 450 error code (while it receives a 550 error code) I think it should be: - it should give a 550 error code (because it did receive a 550 error code from a server downstream) With kind regards, Mark Scholten
From: Wietse Venema on 30 Apr 2010 14:17 Mark Scholten: > Hello, > > Should a system that gives the following response to a SMTP request give a > code 450 error or a code 550 error (I did think a code 550 should be given). > > (host mxfilter4.domain.net[70.34.y.z] said: 450 4.1.1 <user(a)domein.nl>: > Recipient address rejected: undeliverable address: host > mail.domein.nl[70.34.x.y] said: 550 "Unknown User" (in reply to RCPT TO > command) (in reply to RCPT TO command)) > > I did change domain names and the email address and IP addresses (as they > aren't needed in this example and pointing to someone is also something I > don't want to do). > > Is what I suspect correct or are I wrong? > Current situation: > - it gives a 450 error code (while it receives a 550 error code) > I think it should be: > - it should give a 550 error code (because it did receive a 550 error code > from a server downstream) You can configure Postfix to reject such mail or to reply with 4xx. In the latter case you get a chance to make a whitelist entry for sites that send legitimate mail with a non-replyable address. Wietse
From: "Mark Scholten" on 30 Apr 2010 14:23 > -----Original Message----- > From: owner-postfix-users(a)postfix.org [mailto:owner-postfix- > users(a)postfix.org] On Behalf Of Wietse Venema > Sent: Friday, April 30, 2010 8:17 PM > To: Postfix users > Subject: Re: Response codes > > Mark Scholten: > > Hello, > > > > Should a system that gives the following response to a SMTP request > give a > > code 450 error or a code 550 error (I did think a code 550 should be > given). > > > > (host mxfilter4.domain.net[70.34.y.z] said: 450 4.1.1 > <user(a)domein.nl>: > > Recipient address rejected: undeliverable address: host > > mail.domein.nl[70.34.x.y] said: 550 "Unknown User" (in reply to RCPT > TO > > command) (in reply to RCPT TO command)) > > > > I did change domain names and the email address and IP addresses (as > they > > aren't needed in this example and pointing to someone is also > something I > > don't want to do). > > > > Is what I suspect correct or are I wrong? > > Current situation: > > - it gives a 450 error code (while it receives a 550 error code) > > I think it should be: > > - it should give a 550 error code (because it did receive a 550 error > code > > from a server downstream) > > You can configure Postfix to reject such mail or to reply with > 4xx. In the latter case you get a chance to make a whitelist entry > for sites that send legitimate mail with a non-replyable address. > > Wietse Hello Wietse, What is the best option to do in your opinion? Both codes are no problem if I understand you correctly. With kind regards, Mark Scholten
From: Wietse Venema on 30 Apr 2010 14:40 Mark Scholten: > > Mark Scholten: > > > Hello, > > > > > > Should a system that gives the following response to a SMTP request > > give a > > > code 450 error or a code 550 error (I did think a code 550 should be > > given). > > > > > > (host mxfilter4.domain.net[70.34.y.z] said: 450 4.1.1 > > <user(a)domein.nl>: > > > Recipient address rejected: undeliverable address: host > > > mail.domein.nl[70.34.x.y] said: 550 "Unknown User" (in reply to RCPT > > TO > > > command) (in reply to RCPT TO command)) > > > > > > I did change domain names and the email address and IP addresses (as > > they > > > aren't needed in this example and pointing to someone is also > > something I > > > don't want to do). > > > > > > Is what I suspect correct or are I wrong? > > > Current situation: > > > - it gives a 450 error code (while it receives a 550 error code) > > > I think it should be: > > > - it should give a 550 error code (because it did receive a 550 error > > code > > > from a server downstream) > > > > You can configure Postfix to reject such mail or to reply with > > 4xx. In the latter case you get a chance to make a whitelist entry > > for sites that send legitimate mail with a non-replyable address. > > Hello Wietse, > > What is the best option to do in your opinion? Both codes are no problem if > I understand you correctly. In your case you are sending a recipient address verification probe to a down-stream system. Here, replying with 5xx is appropriate, once you have verified that the setup is working properly. In the case of up-stream (sender) address verification, not doing it at all is the appropriate choice for most sites. Up-stream verification is practical only for a site with very little traffic. Wietse
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