Hi there, I recently updated my stunnel installation from 5.70 to the latest 5.82, but an issue has popped up. Nothing else was changed on my system, just stunnel. In my case I use stunnel on an older OS X (yes, that's pre-"macOS") as glue between an outdated Mail client and the world "protected" with modern TLS. Basically Mail connects to stunnel locally which then does the "modern" TLS connection to various provider's mail servers (gmail, etc.) I use 'debug = 4' in stunnel.conf as long nothing is broken. With the old 5.70 the log usually stayed entirely silent that way. Now with 5.82 I see a lot of this: … 2026.10.07 23:03:00 LOG3[871]: transfer_tcp: SSL_read: Connection reset by peer (54) 2026.10.07 23:03:00 LOG3[866]: transfer_tcp: SSL_read: Connection reset by peer (54) 2026.10.07 23:03:00 LOG3[873]: transfer_tcp: SSL_read: Connection reset by peer (54) 2026.10.07 23:03:00 LOG3[869]: transfer_tcp: SSL_read: Connection reset by peer (54) 2026.10.08 01:11:57 LOG3[921]: transfer_tcp: SSL_read: Connection reset by peer (54) 2026.10.08 01:11:57 LOG3[925]: transfer_tcp: SSL_read: Connection reset by peer (54) … It seems to happen to about 20% of all connections/transfers. Investigating further with 'debug = 4' disabled/commented out: … 2026.10.06 18:33:50 LOG5[11]: Connection closed: 85 byte(s) sent to TLS, 264 byte(s) sent to socket 2026.10.06 18:33:50 LOG3[12]: transfer_tcp: SSL_read: Connection reset by peer (54) 2026.10.06 18:33:50 LOG5[12]: Connection reset: 85 byte(s) sent to TLS, 264 byte(s) sent to socket 2026.10.06 18:33:50 LOG3[13]: transfer_tcp: SSL_read: Connection reset by peer (54) 2026.10.06 18:33:50 LOG5[13]: Connection reset: 85 byte(s) sent to TLS, 264 byte(s) sent to socket … Note: #11 is OK, #12 and #13 have the error. Considering they all do the same: contact the server, ask for new mail, and (usually) get an answer of "no new mail" it looks like the error randomly pops up when things are finished? I don't notice any problems inside the Mail client, so all is OK at that end at least. I'm not sure if there's an actual problem here or if this is purely log noise. Any help appreciated. Thanks! regards, H. Thiele -- (a streamlined part of my stunnel.conf for reference) setuid = nobody setgid = nogroup foreground = yes output = /var/log/stunnel.log syslog = no debug = 4 client = yes CAfile = /usr/local/etc/openssl/cert.pem verifyChain = yes sslVersionMin = TLSv1.3 delay = yes [gmx-pop3] accept = 127.0.0.1:41001 connect = pop.gmx.com:995 checkHost = pop.gmx.com [gmx-smtp] accept = 127.0.0.1:41002 connect = mail.gmx.com:465 checkHost = mail.gmx.com [webde-pop3] accept = 127.0.0.1:41003 connect = pop3.web.de:995 checkHost = pop3.web.de [webde-smtp] accept = 127.0.0.1:41004 connect = smtp.web.de:465 checkHost = smtp.web.de [yahoo-pop3] accept = 127.0.0.1:41005 connect = pop.mail.yahoo.com:995 checkHost = pop.mail.yahoo.com [yahoo-smtp] accept = 127.0.0.1:41006 connect = smtp.mail.yahoo.com:465 checkHost = smtp.mail.yahoo.com [gmail-pop3] accept = 127.0.0.1:41007 connect = pop.gmail.com:995 checkHost = pop.gmail.com [gmail-smtp] accept = 127.0.0.1:41008 connect = smtp.gmail.com:465 checkHost = smtp.gmail.com [t-online-pop3] accept = 127.0.0.1:41009 connect = securepop.t-online.de:995 checkHost = securepop.t-online.de [t-online-smtp] accept = 127.0.0.1:41010 connect = securesmtp.t-online.de:465 checkHost = securesmtp.t-online.de ; … [cut the rest of the file for privacy reasons, but more services like above follow here] …