Looking forward to see if someone has an answer. I am encountering the same problem using hotmail. In my case it appears that stunnel is connecting with the outlook server but I never receive an email back.
From: sburke--- via stunnel-users <stunnel-users@stunnel.org>
Sent: Tuesday, September 20, 2022 5:08 AM
To: stunnel-users@stunnel.org <stunnel-users@stunnel.org>
Subject: [stunnel-users] error:0A000126:SSL routines::unexpected eof while reading
 
Hello,
I am trying to get a system notification email back up and running after google disabled the "use less secure apps" functionality in the Gmail platform.
I have set up the Gmail account to use an app password which I assigned to the system that was sending emails before this change. It appears the system is now connecting to Stunnel running on a windows 10 machine and Stunnel is making the connection with the Gmail server again, but no email actually gets sent out.
I am running Stunnel 5.66
Here is the configuration currently:

[gmail-smtp]
client = yes
accept = 25
connect = smtp.gmail.com:465
verifyChain = yes
CAfile = ca-certs.pem
checkHost = smtp.Gmail.com
OCSPaia = yes
 
Here is a copy of the log file:

2022.09.20 07:40:49 LOG5[0]: Service [gmail-smtp] accepted connection from 192.168.100.200:56399
2022.09.20 07:40:49 LOG5[0]: s_connect: connected 74.125.138.109:465
2022.09.20 07:40:49 LOG5[0]: Service [gmail-smtp] connected remote server from 172.16.4.220:60367
2022.09.20 07:40:49 LOG5[0]: OCSP: Connecting the AIA responder "http://ocsp.pki.goog/gtsr1"
2022.09.20 07:40:50 LOG5[0]: s_connect: connected 142.251.40.67:80
2022.09.20 07:40:50 LOG5[0]: OCSP: Certificate accepted
2022.09.20 07:40:50 LOG5[0]: OCSP: Connecting the AIA responder "http://ocsp.pki.goog/gts1c3"
2022.09.20 07:40:50 LOG5[0]: s_connect: connected 142.251.40.67:80
2022.09.20 07:40:50 LOG5[0]: OCSP: Certificate accepted
2022.09.20 07:40:50 LOG5[0]: Certificate accepted at depth=0: CN=smtp.gmail.com
2022.09.20 07:40:51 LOG3[0]: SSL_read: ssl/record/rec_layer_s3.c:308: error:0A000126:SSL routines::unexpected eof while reading
2022.09.20 07:40:51 LOG5[0]: Connection reset: 92 byte(s) sent to TLS, 620 byte(s) sent to socket

Is this something I can remedy from the configuration, or is this something that requires modification on the email server side?

Thank you
sean
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