Potential Greylisting issue

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El_Rapha

New Member
Aug 11, 2026
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Hi the community,
I am facing with a non received email from a sender, let's call it X. X use laposte.net as email provider.
I have 3 mail addresses, one is google and X can, send me emails. Two other addresses are protected by Proxmox Mail Gateway, one is a paid service, I can not manage the configuration and the last one is a self-hosted email on my own domain. I manage the PMG of the last one.
I found a problem I don't understand with the greylisting. Look at the logs :


/var/log/mail.log.1:2026-08-07T13:53:00.654501+02:00 pmg postfix/smtpd[118571]: NOQUEUE: reject: RCPT from [B]smtp-outgoing-1802.laposte.net[/B][160.92.124.[B]103[/B]]: 450 4.7.1 <[EMAIL]raphael@domaine.destinataire.example[/EMAIL]>: Recipient address rejected: Service is unavailable (try later); from=<[EMAIL]expediteur@laposte.net[/EMAIL]> to=<[EMAIL]raphael@domaine.destinataire.example[/EMAIL]> proto=ESMTP helo=<smtp-outgoing-1802.laposte.net>
/var/log/mail.log.1:2026-08-07T14:03:43.179774+02:00 pmg postfix/smtpd[118765]: NOQUEUE: reject: RCPT from [B]smtp-outgoing-1901.laposte.net[/B][160.92.124.[B]105[/B]]: 450 4.7.1 <[EMAIL]raph@domaine.destinataire.example[/EMAIL]>: Recipient address rejected: Service is unavailable (try later); from=<[EMAIL]expediteur@laposte.net[/EMAIL]> to=<[EMAIL]raph@domaine.destinataire.example[/EMAIL]> proto=ESMTP helo=<smtp-outgoing-1901.laposte.net>

As you can see, X emailed me and that was rejected by greylisting I guess. The stmp did another try 10 minutes later. But for this second try, the url has changed and the ip address too.
As my greylistmask4=24, the email shoudn't have been delivered? I never received the email on my 2 addresses protected by Proxmox Mail Gateway. If I deactivate PMG, the mails are received.
What do you think bout this issue?

PS: sorry for my poor english...
 
Welcome to the forum, @El_Rapha
Depending on the minimal required delay configured in greylisting, retrying after 10 minutes may possibly be too early.
Anyway, didn't laposte.net try to deliver more than 2 times? It should. If not, it's not proceeding correctly.
 
I'll check again but I dont think. But if laposte.net try another time with a new URL and IP, will it be identified as a retry or will it be considered as a new message?
The number of tentative can change something if IP and URL are different each time? And what about the greylistmask setting?
 
And it seems I have the same problem with openai :

/var/log/mail.log.1:2026-08-08T19:47:09.888496+02:00 pmg postfix/smtpd[9172]: NOQUEUE: reject: RCPT from o45.ptr3779.openai.com[134.128.96.43]: 450 4.7.1 <recipient@domain.example>: Recipient address rejected: Service is unavailable (try later); from=<bounces+20216706-a6d0-recipient=domain.exsmple@em7877.tm.openai.com> to=<sender@domain.example> proto=ESMTP helo=<o45.ptr3779.openai.com>
/var/log/mail.log.1:2026-08-08T19:47:38.905574+02:00 pmg postfix/smtpd[9172]: NOQUEUE: reject: RCPT from o46.ptr554.openai.com[134.128.96.98]: 450 4.7.1 <recipient@domain.example>: Recipient address rejected: Service is unavailable (try later); from=<bounces+20216706-a6d0-recipient=domain.example@em7877.tm.openai.com> to=<recipiemt@domain.example> proto=ESMTP helo=<o46.ptr554.openai.com>
/var/log/mail.log.1:2026-08-08T19:48:50.950945+02:00 pmg postfix/smtpd[9172]: NOQUEUE: reject: RCPT from o46.ptr554.openai.com[134.128.96.98]: 450 4.7.1 <recipient@domain.example>: Recipient address rejected: Service is unavailable (try later); from=<bounces+20216706-a6d0-recipient=domain.example@em7877.tm.openai.com> to=<recipient@domain.example> proto=ESMTP helo=<o46.ptr554.openai.com>
/var/log/mail.log.1:2026-08-08T19:50:17.941039+02:00 pmg postfix/smtpd[9172]: NOQUEUE: reject: RCPT from o13.ptr1681.openai.com[159.183.12.231]: 450 4.7.1 <recipient@domain.example>: Recipient address rejected: Service is unavailable (try later); from=<bounces+20216706-a6d0-recipient=domain.exampleh@em7877.tm.openai.com> to=<recipient@domain.example> proto=ESMTP helo=<o13.ptr1681.openai.com>
/var/log/mail.log.1:2026-08-08T19:52:31.773351+02:00 pmg postfix/smtpd[9204]: NOQUEUE: reject: RCPT from o14.ptr1360.openai.com[159.183.120.121]: 450 4.7.1 <recipient@domain.example>: Recipient address rejected: Service is unavailable (try later); from=<bounces+20216706-a6d0-recipient=domain.example@em7877.tm.openai.com> to=<sender@domain.example> proto=ESMTP helo=<o14.ptr1360.openai.com>
 
Last edited:
El_Rapha said:
I'll check again but I dont think. But if laposte.net try another time with a new URL and IP, will it be identified as a retry or will it be considered as a new message?
Click to expand...
It depends on whether a next try is from the IP address from the same IP network range as included by the netmask configured in you server.

But no matter if yes or no, the sending machine should try more times.
El_Rapha said:
The number of tentative can change something if IP and URL are different each time?
Click to expand...
I'm afraid I don't understand this sentence.
 
Onslow said:
It depends on whether a next try is from the IP address from the same IP network range as included by the netmask configured in you server.

But no matter if yes or no, the sending machine should try more times.

I'm afraid I don't understand this sentence.
Click to expand...
I mean that even if the smtp tried more, as the IP change each time, all tentatives will be seen as independent mail, so they will be blocked.
 
@El_Rapha, I get the impression that you don't read my replies carefully.
1) Retrying after only 10 minutes may possibly be too early.
2) open.ai retries were in a 5 minutes span - almost surely too early.
3) I'm repeating the question: were retries later?
 
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