Andrew C Aitchison wrote:
> On Wed, 28 Sep 2022, Victor Sudakov via Exim-users wrote:
>
> > Dear Colleagues,
> >
> > Has anyone had problems recently sending to aspmx.l.google.com ?
>
> Yes. This is a known issue
> https://bugs.exim.org/show_bug.cgi?id=2907
>
> The bug is not actually in exim, but in Linux kernel TCP Fast Open code
> shipped by at least Debian.
Thank you, Andrew! I had been unable to google up the problem for some
reason.
Setting `sysctl net.ipv4.tcp_fastopen=0` has helped and the mail in
question has been delivered. At least this proves the real cause of the problem.
I wonder what I will lose if I leave net.ipv4.tcp_fastopen=0 on the
mail server (not very loaded)?
--
Victor Sudakov VAS4-RIPE
http://vas.tomsk.ru/
2:5005/49@fidonet
