I have one connection that works, and another which fails; but they have equivalent settings. Please help me resolve this. A fragment of the config for the connection that works: [Lopham-smtp] client = yes accept = 127.0.0.1:52025 connect = mail.lopham.co.uk:465 The server mail.lopham.co.uk is hosted by a service that I pay for. A fragment of the config for the connection that fails: [zen-smtp] client = yes accept = 127.0.0.1:26025 connect = mailhost.zen.co.uk:587 The failure in the log is 2026.06.02 12:22:48 LOG3[1]: SSL_connect: Connection reset by peer (WSAECONNRESET) (10054). The server mailhost.zen.co.uk is hosted by my internet connection provider (Zen Internet). When I make the connection without using stunnel the connection works OK. My SMTP settings in Outlook 2010 are: Server = mailhost.zen.co.uk Authentication = Yes Port = 576 Encryption = TLS So I set debug = 7 The log shows: 2026.06.02 12:22:48 LOG7[1]: Service [zen-smtp] started 2026.06.02 12:22:48 LOG7[1]: Setting local socket options (FD=504) 2026.06.02 12:22:48 LOG7[1]: Option TCP_NODELAY set on local socket 2026.06.02 12:22:48 LOG5[1]: Service [zen-smtp] accepted connection from 127.0.0.1:53292 2026.06.02 12:22:48 LOG6[1]: failover: priority, starting at entry #0 2026.06.02 12:22:48 LOG6[1]: s_connect: connecting 212.23.1.19:587 2026.06.02 12:22:48 LOG7[1]: s_connect: s_poll_wait 212.23.1.19:587: waiting 10 seconds 2026.06.02 12:22:48 LOG7[1]: FD=468 ifds=rw ofds=-- 2026.06.02 12:22:48 LOG5[1]: s_connect: connected 212.23.1.19:587 2026.06.02 12:22:48 LOG5[1]: Service [zen-smtp] connected remote server from 127.0.0.1:53293 2026.06.02 12:22:48 LOG7[1]: Setting remote socket options (FD=468) 2026.06.02 12:22:48 LOG7[1]: Option TCP_NODELAY set on remote socket 2026.06.02 12:22:48 LOG7[1]: Remote descriptor (FD=468) initialized 2026.06.02 12:22:48 LOG6[1]: SNI: sending servername: mailhost.zen.co.uk 2026.06.02 12:22:48 LOG7[1]: No previous session to resume 2026.06.02 12:22:48 LOG6[1]: Peer certificate required 2026.06.02 12:22:48 LOG7[1]: TLS state (connect): before SSL initialization 2026.06.02 12:22:48 LOG7[1]: TLS state (connect): SSLv3/TLS write client hello 2026.06.02 12:22:48 LOG3[1]: SSL_connect: Connection reset by peer (WSAECONNRESET) (10054) 2026.06.02 12:22:48 LOG5[1]: Connection reset: 0 byte(s) sent to TLS, 0 byte(s) sent to socket 2026.06.02 12:22:48 LOG7[1]: remote_fd reset (FD=468) 2026.06.02 12:22:48 LOG7[1]: Remote descriptor (FD=468) closed 2026.06.02 12:22:48 LOG7[1]: local_rfd/local_wfd reset (FD=504) 2026.06.02 12:22:48 LOG7[1]: Local descriptor (FD=504) closed 2026.06.02 12:22:48 LOG7[1]: Service [zen-smtp] finished (0 left) The log does not show me why the connection is reset by the peer. Can anybody help, please? Regards, == Graham