1 Topic by RikuS (edited by RikuS 2016-11-08 19:45:45)

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Topic: Local sender gets no error message (450 4.7.0)

======== Required information ====
- iRedMail version (check /etc/iredmail-release): 0.9.5-1
- Linux/BSD distribution name and version: CentOS 7.2
- Store mail accounts in which backend (LDAP/MySQL/PGSQL):  MySQL
- Web server (Apache or Nginx): Nginx
- Manage mail accounts with iRedAdmin-Pro? no
- Related log if you're reporting an issue: mail.log
====

Hi!

I have an issue that I coudn't solve by myself. Email user sent an email, that was blocked byu recipient server. Recipient server sent 450 4.7.0 error (message delivery has been blocked), but sender didn't get any message about this to inbox, we only could find this information on logs.

iRedMail server tried to send this message for about next 20 hours without success, without any notification to user. Is this normal that local sender doesn't get any bounce message on this error?

Oct 28 07:49:00 posti postfix/qmgr[20394]: 11E8260497: from=<sender@domain.ltd>, size=5766, nrcpt=1 (queue active)

Oct 28 07:49:00 posti postfix/smtp[32410]: Anonymous TLS connection established to mx57392.pri.secmail.com[217.112.192.18]:25: TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)

Oct 28 07:49:00 posti postfix/smtp[32410]: 11E8260497: host mx57392.pri.secmail.com[217.112.192.18] said: 450 4.7.0 Message delivery has been blocked. If you think this is an error, you can check the details and make a difference at http://www.secmail.com/c/451/68870971827.html (in reply to RCPT TO command)

Oct 28 07:49:01 posti postfix/smtp[32410]: Anonymous TLS connection established to mx57392.pri.secmail.com[217.112.192.16]:25: TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)

Oct 28 07:49:01 posti postfix/smtp[32410]: 11E8260497: to=<recipient@anotherdomain.ltd>, relay=mx57392.pri.secmail.com[217.112.192.16]:25, delay=67799, delays=67798/0.05/1.1/0.07, dsn=4.7.0, status=deferred (host mx57392.pri.secmail.com[217.112.192.16] said: 450 4.7.0 Message delivery has been blocked. If you think this is an error, you can check the details and make a difference at http://www.secmail.com/c/451/73224057346.html (in reply to RCPT TO command))

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2 Reply by ZhangHuangbin

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Re: Local sender gets no error message (450 4.7.0)

RikuS wrote:

iRedMail server tried to send this message for about next 20 hours without success, without any notification to user. Is this normal that local sender doesn't get any bounce message on this error?

This is normal because the recipient server sent smtp code '450' instead of '5xx'.

450 (4xx) means a temporarily issue and sender server should retry. 5xx means a permanent error and sender server should stop retry and notify sender.

So, it's a recipient server issue caused by its sys admin, not iRedMail.

3 Reply by RikuS (edited by RikuS 2016-11-08 19:53:40)

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Re: Local sender gets no error message (450 4.7.0)

ZhangHuangbin wrote:
RikuS wrote:

iRedMail server tried to send this message for about next 20 hours without success, without any notification to user. Is this normal that local sender doesn't get any bounce message on this error?

This is normal because the recipient server sent smtp code '450' instead of '5xx'.

450 (4xx) means a temporarily issue and sender server should retry. 5xx means a permanent error and sender server should stop retry and notify sender.

So, it's a recipient server issue caused by its sys admin, not iRedMail.

Thanks! So even if sending fails complete after trying enough, there will be no notification to sender that message could not be delivered at all?

Recipient server admin told me that, sender servers should usually notify after some period of time if mail couldn't be delivered, and also after senders server stops trying to deliver completely.

4 Reply by ZhangHuangbin

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Re: Local sender gets no error message (450 4.7.0)

RikuS wrote:

So even if sending fails complete after trying enough, there will be no notification to sender that message could not be delivered at all?

Postfix (the MTA) will notify sender after it tried enough times and the email exceeds the queue time: http://www.postfix.org/postconf.5.html# … e_lifetime

RikuS wrote:

Recipient server admin told me that, sender servers should usually notify after some period of time if mail couldn't be delivered, and also after senders server stops trying to deliver completely.

This is true. Please try commands below:

postconf -e delay_warning_time=1h
postfix reload

"1h" means if the email has been stalled in queue for 1 hour, Postfix will send a notification to sender.

We should consider this as a iRedMail bug, i will enable this in next iRedMail release by default. But back to the topic, if recipient server admin really want to block someone, please use '5xx' smtp code. You'd better ask him/her to update it.

5 Reply by RikuS

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Re: Local sender gets no error message (450 4.7.0)

Perfect, thanks!

Does postfix include this error code and message (450 4.7.0 Message delivery has been blocked...) to sender when configured delay_warning_time or/and maximal_queue_lifetime was reached?

About recipient blocking: this recipient uses system that can block incoming mail with 4xx code, and server answer includes link where sender can unblock that mail. Legitimate sender should get this server reply so they can act based on that and release blocked mail. This mail on original post was blocked, because our server is in network that has been used for spamming before.

6 Reply by ZhangHuangbin

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Re: Local sender gets no error message (450 4.7.0)

RikuS wrote:

Does postfix include this error code and message (450 4.7.0 Message delivery has been blocked...) to sender when configured delay_warning_time or/and maximal_queue_lifetime was reached?

I cannot remember sad You can give it a try. I suppose not.

RikuS wrote:

About recipient blocking: this recipient uses system that can block incoming mail with 4xx code, and server answer includes link where sender can unblock that mail. Legitimate sender should get this server reply so they can act based on that and release blocked mail. This mail on original post was blocked, because our server is in network that has been used for spamming before.

Just one thing: if you want to BLOCK me, then don't ask me to retry delivery --> Use 5xx instead of 4xx please.

7 Reply by RikuS

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Re: Local sender gets no error message (450 4.7.0)

ZhangHuangbin wrote:

I cannot remember sad You can give it a try. I suppose not.

Thanks alot, I'll play around with this soon.

ZhangHuangbin wrote:

Just one thing: if you want to BLOCK me, then don't ask me to retry delivery --> Use 5xx instead of 4xx please.

Sadly I have no control over their server, so they block people any way they want sad

I sure owe you a coffee now smile