Bug#1031718: In some cases there is the error: connection refused (Socket error code 10061)

[Debian]

Package: libgnutls30
X-Debbugs-Cc: debian at decotrain.de
Version: 3.7.1-5+deb11u2
Severity: normal

Hello,

this is more a question for ideas and support, because a bug cannot be 
proven.

There is a problem with the mail system on a server, that does not 
receive emails from certain providers any more.
The sender of the emails don't get any notice that the emails are not 
delivered and there is only one sender that could provide an error 
message. This is:

2/17/2023 12:43:19 PM - Server at PAWP195MB2418.EURP195.PROD.OUTLOOK.COM 
returned '550 5.4.316 Message expired, connection refused(Socket error 
code 10061)'
2/17/2023 12:33:05 PM - Server at domain.de (xx.79.98.xx) returned '450 
4.4.316 Connection refused [Message=Socket error code 10061]

Searching the internet shows that will be caused by a routing problem, 
but the mail system generally works and emails are received from other 
senders.

The problem exists since 2023-02-15 so the idea is to search what has 
changed.
The only thing that has changed is that an automated security update has 
happened:

Start-Date: 2023-02-15 07:38:27
Commandline: apt-get upgrade -y -o 
Dir::Etc::SourceList=/etc/apt/security.sources.list
Upgrade: libgnutls30:amd64 (3.7.1-5+deb11u2, 3.7.1-5+deb11u3), 
libgnutls-dane0:amd64 (3.7.1-5+deb11u2, 3.7.1-5+deb11u3)
End-Date: 2023-02-15  07:38:32

That's the reason why the question is placed here.

The changelog only tells about an "Fix double free":
https://metadata.ftp-master.debian.org/changelogs//main/g/gnutls28/gnutls28_3.7.1-5+deb11u2_changelog

It makes no sense that this bug was needed to avoid routing problems!?

Is there any other idea for the reason of the problem?

Best regards
karsten


-- System Information:
Debian Release: 11.6
  APT prefers stable-updates
  APT policy: (500, 'stable-updates'), (500, 'stable-security'), (500, 
'proposed-updates'), (500, 'stable')
Architecture: amd64 (x86_64)
Foreign Architectures: i386

Kernel: Linux 5.10.0-21-amd64 (SMP w/4 CPU threads)
Kernel taint flags: TAINT_PROPRIETARY_MODULE, TAINT_OOT_MODULE, 
TAINT_UNSIGNED_MODULE
Locale: LANG=de_DE.UTF-8, LC_CTYPE=de_DE.UTF-8 (charmap=UTF-8), LANGUAGE 
not set
Shell: /bin/sh linked to /bin/dash
Init: systemd (via /run/systemd/system)
LSM: AppArmor: enabled
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