Re: [exim] TLS connection with Microsoft server stalls

On 25/09/2020 10:26, Christian Eyrich via Exim-users wrote:
> I’ve sent mails from @outlook.de to my server but the TLS encrypted
> communication just stops at one point after some progress through EHLO,
> MAIL FROM, RCPT TO (exim -bd -d+all):
>
> 10:04:45 15402 SMTP>> 250 Accepted
> 10:04:45 15402 tls_write(0x558a49151ac0, 14)
> 10:04:45 15402 gnutls_record_send(SSL, 0x558a49151ac0, 14)
> 10:04:45 15402 outbytes=14
> 10:04:45 15402 DSN: orcpt: NULL  flags: 0
> 10:04:45 15402 Calling gnutls_record_recv(0x558a4920e660,
> 0x558a494e9000, 4096)
>
> Then after 300 seconds the connection is closed.
>
> This is with Exim 4.92, GnuTLS 3.6.7 from Debian Buster.
> I already stripped away every config change I did for TLS ciphers or DH
> params.
>
> I know it worked in the past. And it still works without TLS. Maybe it’s
> a problem of GnuTLS or maybe on Microsoft side, supposedly in some edge
> scenario. But how can I debug it further?

There may be a bit of debug output earlier on, during the TLS handshake,
talking about the session secrets. If so, fire up wireshark.

If not, compile yourself a current Exim from git, first.

What we're looking for is the encrypted version of that write going
out on the wire - and whether there is any response of any kind, on
the wire.
--
Cheers,
Jeremy