On 2022-06-01 11:05, Rory Campbell-Lange wrote:
> My company's servers are having some curious issues sending some email to
google, running exim on Debian.
>
>
> The error seems unique to sending to google; we are sending around 12.5k
messages/day to a wide variety of recipients.
>
> Any thoughts?
Yes - See:
https://lists.exim.org/lurker/message/20220524.110745.56bc2aa8.en.html
I stumbled over this issue as well, mostly for messages that have
attachments (ie a large amount of DATA, rather than short plain text). I
have added the following config, which appears to have resolved it, though
the packet trace wouldn't indicate that this should be the issue at all.
Google is doing something odd, and apparently (checks exim mainlogs.yep)
fixed by turning off TFO for some reason, despite the issue coming much
later than the TCP open process.
In /etc/exim4/conf.d/transport/30_exim4-config_remote_smtp (Debian system):
hosts_try_fastopen = !*.l.google.com
If you have success or not with it, I'd be interested to know!
Cheers
Graeme
