Re: [exim] Some Emails to gmail now hang

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Author: Viktor Dukhovni
Date:  
To: exim-users
Subject: Re: [exim] Some Emails to gmail now hang
On Wed, Aug 10, 2022 at 04:00:51PM -0700, Marc MERLIN wrote:

> > I've also reached out to the Gmail team. They're aware. Which is not
> > to say that there's a quick fix in the works, the front-end connection
> > termination devices are both non-trivial and critical, so changes will
> > happen cautiously and likely slowly, and may be delayed by other
> > priorities...
>
> Thanks.
>
> Whose fault is it? debian/exim, or gmail?


It looks *strongly* like an interoperability problem between the Linux
kernel TCP implementation and the Google TCP/TLS termination front-ends,
unless all the Exim users who lately somewhat regularly show up to
report this issue are behind some as yet unidentified set of
middle-boxes that break TCP state.

It would perhaps be useful to also see any reports of success sending
sufficiently large messages to Gmail from the reported Exim builds and
Linux versions. If some users are not seeing any issues, then it would
be good to know how their situation is differs.

If you have Exim on a Linux laptop and are able to connect it the office
WiFi network, can you still see the problem with default Exim settings?

Can you post a "tshark" decode of a full capture of a failed delivery?

    # tcpdump -s0 -w /some/file.pcap ...
    # tshark -nr /some/file


[ Keep the PCAP file, more questions may arise once the basic decode is
posted. ]

-- 
    Viktor.