Hello List My problem: If I run stunnel I regular get the below error: [.] stunnel 5.46 on x86-pc-msvc-1500 platform [.] Compiled/running with OpenSSL 1.0.2o-fips 27 Mar 2018 [.] Threading:WIN32 Sockets:SELECT,IPv6 TLS:ENGINE,FIPS,OCSP,PSK,SNI [ ] errno: (*_errno()) [ ] Running on Windows 6.2 [.] Reading configuration from file stunnel.conf [.] UTF-8 byte order mark detected [.] FIPS mode disabled [ ] Compression disabled [ ] No PRNG seeding was required [ ] Initializing service [smtps] [ ] GUI message loop initialized [ ] Ciphers: HIGH:!aNULL:!SSLv2:!DH:!kDHEPSK [ ] TLS options: 0x03000004 (+0x00000000, -0x00000000) [ ] Loading certificate from file: stunnel.pem [ ] Certificate loaded from file: stunnel.pem [ ] Loading private key from file: stunnel.pem [ ] Private key loaded from file: stunnel.pem [ ] Private key check succeeded [:] Service [smtps] needs authentication to prevent MITM attacks [.] Configuration successful [ ] Binding service [smtps] [ ] Listening file descriptor created (FD=676) [ ] Setting accept socket options (FD=676) [ ] Option SO_EXCLUSIVEADDRUSE set on accept socket

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[!] bind: Address already in use (WSAEADDRINUSE) (10048) <<<< [!] Error binding service [smtps] to 192.168.10.62:11465 [!] Could not bind any accepting port [ ] Deallocating section defaults [ ] Unbinding service [smtps] [ ] Service [smtps] closed [ ] Deallocating section [smtps]

I had the same problem with the previous versions aswell. To temporary resolv the problem I have to change the listen port to another number. Reread the config file and let the stunnel GUI open. Then all is working until I close the GUI (not each time but most of). My system: - Windows 2016 Server - stunnel-5.46 - stunnel installed as service and GUI My config file (relevant part): taskbar = yes client=yes [smtps] ;delay = yes accept = 192.168.10.62:11466 connect = server.domain.ch:465 cert = stunnel.pem local = 192.168.10.53 (this is dedicated address) I found a similar threat in the archives (but on Linux): https://www.stunnel.org/pipermail/stunnel-users/2018-February/005935.html Here is Microsoft's describtion about WSAEADDRINUSE) (10048): https://msdn.microsoft.com/en-us/library/windows/desktop/ms740668(v=vs.85).a... All helps are welcome. Kind regards, -- Martin Schweizer PC-Service M. Schweizer GmbH; Bannholzstrasse 6; Postfach 132; CH-8608 Bubikon; Tel. +41 55 243 30 00; Fax: +41 55 243 33 22