On 2022-04-29, Graeme Coates via Exim-users <[email protected]> wrote: > Hi all, > > > > I've seen this issue raised in: > > > > https://lists.exim.org/lurker/message/20220216.071725.892984cd.en.html > > and > > https://lists.exim.org/lurker/message/20220313.200645.624cc373.en.html > > > > but haven't seen a definite resolution as yet. > > > > As per other reports, I have a Debian Bullseye (11.3) system running Exim > 4.94.2 #2. It is setup with virtual domains using dovecot for local delivery > and aliases defined for some simple forwarding. I wasn't aware of any > similar issue in Exim 4.92 (on Debian 10). I see log reports similar to > other reports - eg: > > > > /var/log/exim4/mainlog:2022-04-27 07:47:30 1njbGQ-005LxL-M5 > H=gmail-smtp-in.l.google.com [2a00:1450:4010:c0e::1a]: SMTP timeout after > sending data block (199774 bytes written): Connection timed out > > /var/log/exim4/mainlog:2022-04-27 07:50:10 1njbGU-005Lz8-RV > H=gmail-smtp-in.l.google.com [74.125.131.26]: SMTP timeout after end of data > (246239 bytes written): Connection timed out > > > > This is for both ipv4 and ipv6 connections, and to only Google mail servers, > and only when delivering "large" messages (that are bigger than say about > 100kb, though I haven't investigated fully the limits - short, text only is > fine). Eventually, the messages do get through, but with delays of hours in > some cases. As per other reports, delivery of the same mail to all other > hosts works perfectly. This occurs both with firewall rules set to allow > everything, as well as with a "normal" ruleset allowing: all > OUTBOUND/FORWARD, all icmp INBOUND and all TCP INBOUND with ctstate > RELATED,ESTABLISHED (as well as ports opened for relevant services). > > > > If I do: sysctl net.ipv4.tcp_window_scaling=0 , then everything works > perfectly - with tcp_window_scaling=1, the issue is reproduced. > > > > I have a packet capture which is available here: > > > > https://tinyurl.com/742s855d > > > > The Session log from Exim in debug mode is here (with redacted hosts, > addresses, etc) - the message was delivered to the server, and is being > forwarded onto an email in a Google workspace account (following a > forwarding rule in an aliases file) > > > > https://tinyurl.com/22nn887u > > > > > > Is it possible from these traces to pin down the issue at all and maybe come > up with a workround (without having to turn off tcp_window_scaling) or a > pointer as to where I need to formally raise a bug, and I'll be happy to do > so!
make sure that your DNS and return-path MX are working, we recently had some sort of firewall issue that was unrelated to SMTP causing timeouts on deliveries to gmail. removing the firewall rules cleared it up. -- Jasen. -- ## List details at https://lists.exim.org/mailman/listinfo/exim-users ## Exim details at http://www.exim.org/ ## Please use the Wiki with this list - http://wiki.exim.org/
