Hi Graham,

I was unable to reproduce this issue. I don't have a Windows 7 machine to test, but it should be no difference with Windows 10 or 11.

Can you try updating your [Zen-pop3] config like this: ?

[zen-pop3]
client = yes
accept = 127.0.0.1:110
connect = mailhost.zen.co.uk:995

CAfile = ca-certs.pem

verifyChain = yes
checkHost = mailhost.zen.co.uk
OCSPaia = yes

You can also set debug=5 instead of commenting the line to have the same level log of verbosity.

Let us know how it goes. Thanks.

Regards,

Jose

On Thursday, May 14, 2026 at 08:09:03 AM GMT-5, Graham Jones via stunnel-users <stunnel-users@lists.stunnel.org> wrote:

I'm new to stunnel.

stunnel 5.78 on x64-pc-mingw32-gnu platform

Windows 7 Pro

Using Outlook to open a connection to a POP server

Extract from stunnel.conf

[Zen-pop3]

client = yes

accept = 127.0.0.1:110

connect = mailhost.zen.co.uk:995

CAfile = ca-certs.pem

With debug = 7 the test succeeds. The log shows:

2026.05.13 16:49:06 LOG5[4]: Service [Zen-pop3] accepted connection from

127.0.0.1:49596

2026.05.13 16:49:06 LOG5[4]: s_connect: connected 212.23.1.19:995

2026.05.13 16:49:06 LOG5[4]: Service [Zen-pop3] connected remote server from

127.0.0.1:49598

2026.05.13 16:49:06 LOG5[4]: Connection closed: 59 byte(s) sent to TLS, 202

byte(s) sent to socket

With ;debug a test connection fails after about 20 seconds delay. Log

extract:

2026.05.13 17:22:05 LOG5[6]: Service [Zen-pop3] accepted connection from

127.0.0.1:53162

2026.05.13 17:22:05 LOG5[6]: s_connect: connected 212.23.1.11:995

2026.05.13 17:22:05 LOG5[6]: Service [Zen-pop3] connected remote server from

127.0.0.1:53163

2026.05.13 17:22:26 LOG3[6]: SSL_connect: Connection reset by peer

(WSAECONNRESET) (10054)

Why does it only work with debug enabled?

Any ideas, please?

Regards,

== Graham

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