Issue Problem with greylisting

[mow]

Server operating system version

Debian 11.5 x86_64

Plesk version and microupdate number

Plesk Obsidian 18.0.44.3

Hi,

greylisting seems too strict:

Nov  1 04:07:22 sourcetronic postfix/smtpd[1757448]: connect from server1
Nov  1 04:07:24 sourcetronic postfix/smtpd[1757448]: 31CA612A2AA2: client=server1
Nov  1 04:07:24 sourcetronic psa-pc-remote[5133]: 31CA612A2AA2: from=…
Nov  1 04:07:24 sourcetronic psa-pc-remote[5133]: 31CA612A2AA2: grey: stderr: SKIP
Nov  1 04:07:24 sourcetronic psa-pc-remote[5133]: 31CA612A2AA2: grey: stderr: SKIP
Nov  1 04:07:24 sourcetronic psa-pc-remote[5133]: 31CA612A2AA2: grey: stderr: DEFER
Nov  1 04:07:24 sourcetronic psa-pc-remote[5133]: Message aborted.

Nov  1 04:07:28 sourcetronic postfix/smtpd[1757448]: connect from server2
Nov  1 04:07:29 sourcetronic postfix/smtpd[1757448]: 38C3B12A2AA2: client=server2
Nov  1 04:07:29 sourcetronic psa-pc-remote[5133]: 38C3B12A2AA2: from=…
Nov  1 04:07:29 sourcetronic psa-pc-remote[5133]: 38C3B12A2AA2: grey: stderr: DEFER
Nov  1 04:07:29 sourcetronic psa-pc-remote[5133]: Message aborted.

Nov  1 04:15:06 sourcetronic postfix/smtpd[1757644]: connect from server2
Nov  1 04:15:07 sourcetronic postfix/smtpd[1757644]: CD34712A2AA2: client=server2
Nov  1 04:15:07 sourcetronic psa-pc-remote[5133]: CD34712A2AA2: from=…
Nov  1 04:15:07 sourcetronic psa-pc-remote[5133]: CD34712A2AA2: grey: stderr: SKIP
Nov  1 04:15:07 sourcetronic psa-pc-remote[5133]: CD34712A2AA2: grey: stderr: DEFER
Nov  1 04:15:07 sourcetronic psa-pc-remote[5133]: Message aborted.

Nov  1 04:25:06 sourcetronic postfix/smtpd[1757829]: connect from server2
Nov  1 04:25:07 sourcetronic postfix/smtpd[1757829]: EA6E912A2AA2: client=server2
Nov  1 04:25:07 sourcetronic psa-pc-remote[5133]: EA6E912A2AA2: from=…
Nov  1 04:25:07 sourcetronic psa-pc-remote[5133]: EA6E912A2AA2: grey: stderr: SKIP
Nov  1 04:25:07 sourcetronic psa-pc-remote[5133]: EA6E912A2AA2: grey: stderr: SKIP
Nov  1 04:25:08 sourcetronic psa-pc-remote[5133]: EA6E912A2AA2: grey: stderr: DEFER
Nov  1 04:25:08 sourcetronic psa-pc-remote[5133]: Message aborted.

(tl;dr: sending provider connects first from one IP, then three times from another, then the sender gives up)

What is interesting: On the first attempt, grey results in SKIP, SKIP, DEFER, on the next attempt with the other IP it immediately goes to DEFER, then SKIP, DEFER, then SKIP, SKIP, DEFER, and I'd guess the next attempt, if it came, would be SKIP, SKIP, SKIP and go through.

Now, why would Plesk do that? What is the meaning of the first and second check? (I guess the third is the connection database check recognizing the previous attempt.)
Penalty for reconnecting too fast is supposed to be switched off, and could only be valid for the second attempt anyway, but not the third or fourth:
Penalty interval 2 minutes Penalty disabled