# Postgrey testing

**URL:** <https://discourse.mailinabox.email/t/postgrey-testing/8542>\
**Category:** Maintenance\
**Created:** [November 14, 2021, 1:33pm UTC](https://discourse.mailinabox.email/t/postgrey-testing/8542 "2021-11-14T13:33:02Z")\
**Posts on this page:** 8\
**Page:** 1

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**Author:** ![stefbishop](https://discourse.mailinabox.email/letter_avatar_proxy/v4/letter/s/0ea827/32.png) [@stefbishop](https://discourse.mailinabox.email/u/stefbishop)\
**Post date:** [November 14, 2021, 1:33pm UTC](https://discourse.mailinabox.email/t/postgrey-testing/8542/1 "2021-11-14T13:33:03Z")

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Hi,  
I was investigating an email that reportedly didn’t get received my system. The same sender did manage to send an email some days later.  
It seems the original message was postgreyed, but the sending email server didn’t try again.  
The email servers for the 2 emails were different.

My question is. is there a way of probing a foreign mailserver to see if it respects the postgrey protocol?

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**Author:** ![openletter](https://discourse.mailinabox.email/letter_avatar_proxy/v4/letter/o/f1d935/32.png) [@openletter](https://discourse.mailinabox.email/u/openletter)\
**Post date:** [November 14, 2021, 1:34pm UTC](https://discourse.mailinabox.email/t/postgrey-testing/8542/2 "2021-11-14T13:34:34Z")

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Postgrey follows RFCs. If a server has been configured to not follow RFCs, you can’t know other than trial and error.

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**Author:** ![stefbishop](https://discourse.mailinabox.email/letter_avatar_proxy/v4/letter/s/0ea827/32.png) [@stefbishop](https://discourse.mailinabox.email/u/stefbishop)\
**Post date:** [November 14, 2021, 1:35pm UTC](https://discourse.mailinabox.email/t/postgrey-testing/8542/3 "2021-11-14T13:35:46Z")

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The mail log showed this for the first email…

> Oct 25 12:28:54 dcwmail postfix/smtpd[15440]: connect from [mailomta4-sa.btinternet.com](http://mailomta4-sa.btinternet.com)[213.120.69.10]  
> Oct 25 12:28:54 dcwmail postfix/smtpd[15440]: warning: restriction `reject\_authenticated\_sender\_login\_mismatch’ ignored: no SASL support  
> Oct 25 12:28:54 dcwmail postgrey[15793]: action=greylist, reason=new, client\_name=[mailomta4-sa.btinternet.com](http://mailomta4-sa.btinternet.com), client\_address=213.120.69.10/32, [sender=mc.xxxxxxx@btinternet.com](mailto:sender=mc.xxxxxxx@btinternet.com), [recipient=peter@peterxxxxxxx.com](mailto:recipient=peter@peterxxxxxxx.com)  
> Oct 25 12:28:54 dcwmail postfix/smtpd[15440]: NOQUEUE: reject: RCPT from [mailomta4-sa.btinternet.com](http://mailomta4-sa.btinternet.com)[213.120.69.10]: 450 4.2.0 [peter@peterxxxxxxx.com](mailto:peter@peterxxxxxxx.com): Recipient address rejected: Greylisted, see [Postgrey Help](http://postgrey.schweikert.ch/help/peterxxxxxxx.com.html); from=[mc.xxxxxxx@btinternet.com](mailto:mc.xxxxxxx@btinternet.com) to=[peter@peterxxxxxxx.com](mailto:peter@peterxxxxxxx.com) proto=ESMTP helo=\<[sa-prd-fep-046.btinternet.com](http://sa-prd-fep-046.btinternet.com)\>  
> Oct 25 12:28:54 dcwmail postfix/smtpd[15440]: disconnect from [mailomta4-sa.btinternet.com](http://mailomta4-sa.btinternet.com)[213.120.69.10] ehlo=2 starttls=1 mail=1 rcpt=0/1 rset=1 quit=1 commands=6/7

The successful email came from [mailomta8-re.btinternet.com](http://mailomta8-re.btinternet.com)

Thanks  
Stef Bishop

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**Author:** ![stefbishop](https://discourse.mailinabox.email/letter_avatar_proxy/v4/letter/s/0ea827/32.png) [@stefbishop](https://discourse.mailinabox.email/u/stefbishop)\
**Post date:** [November 14, 2021, 1:40pm UTC](https://discourse.mailinabox.email/t/postgrey-testing/8542/4 "2021-11-14T13:40:50Z")

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Thanks. I guess only an appeal to the hostmaster concerned would work. Maybe in their interest to know.

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**Author:** ![openletter](https://discourse.mailinabox.email/letter_avatar_proxy/v4/letter/o/f1d935/32.png) [@openletter](https://discourse.mailinabox.email/u/openletter)\
**Post date:** [November 14, 2021, 1:42pm UTC](https://discourse.mailinabox.email/t/postgrey-testing/8542/5 "2021-11-14T13:42:19Z")

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When the mail comes from different mail servers, Postgrey treats each as a new server.

You can use the whitelist feature if this is a regular problem.

I made this guide. It covers one specific scenario and the solution may not perfectly align with your problem, but the general idea of using a whitelist is what I was hoping to communicate:

> [@How to use Postgrey client whitelists](https://discourse.mailinabox.email/t/how-to-use-postgrey-client-whitelists/8355):
>
> The Postfix Greylisting Policy Server (Postgrey) uses the concept of greylisting to take advantage of mail standards that the vast majority of spammers are not or cannot be configured to support. The postfix process is configured to send incoming mail to postgrey, which determines whether the mail can continue to the next step in the delivery process by checking whether the sender (“client”) or recipient match anything postgrey is configured to match. When the postgrey test fails, postfix will…

Odds are their admins already know about the problem and don’t care to fix it.

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**Author:** ![stefbishop](https://discourse.mailinabox.email/letter_avatar_proxy/v4/letter/s/0ea827/32.png) [@stefbishop](https://discourse.mailinabox.email/u/stefbishop)\
**Post date:** [November 14, 2021, 1:53pm UTC](https://discourse.mailinabox.email/t/postgrey-testing/8542/6 "2021-11-14T13:53:29Z")

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Thanks.  
I’ve put it down to a one off occurence. I will only worry about it if it happens again!  
Cheers

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**Author:** ![openletter](https://discourse.mailinabox.email/letter_avatar_proxy/v4/letter/o/f1d935/32.png) [@openletter](https://discourse.mailinabox.email/u/openletter)\
**Post date:** [November 14, 2021, 1:56pm UTC](https://discourse.mailinabox.email/t/postgrey-testing/8542/7 "2021-11-14T13:56:17Z")

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Likely it will occur with email from the provider. They have numerous MTAs and don’t bother to configure them to resend using the same server.

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**Author:** ![system](https://discourse.mailinabox.email/uploads/default/original/2X/4/4d0933d13c456b7e57f296aa6cc344525b6f0c70.png) [@system](https://discourse.mailinabox.email/u/system)\
**Post date:** [December 24, 2021, 1:56pm UTC](https://discourse.mailinabox.email/t/postgrey-testing/8542/8 "2021-12-24T13:56:37Z")

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