Hi List,

I have just joined the stunnel community.

I am in the process of migrating our mailserver's public facing ports to stunnel for PCI compliance reasons.

So far i have managed to get working:

- imap (143/tcp) with starttls

- imaps (993/tcp)

- pop3 (110/tcp) with starttls

- pop3s (995/tcp)

My trouble is with smtp(25/tcp,587/tcp) with starttls.

I have now tried a couple different mail clients and everyone of them tells me that the server does not support the authentication protocols.

I have installed stunnel 5.44. Tee relevant parts in my config:

[mail2-imap]
protocol = imap
accept = 143
connect = <mail-fqdn>:143

[mail2-imaps]
accept = 993
connect = <mail-fqdn>:143

[mail2-pop3]
protocol = pop3
accept = 110
connect = <mail-fqdn>:110

[mail2-pop3s]
accept = 995
connect = <mail-fqdn>:110

[mail2-smtp]
protocol = smtp
accept = 25
connect = <mail-fqdn>:25

[mail2-smtps]
accept = 465
connect = <mail-fqdn>:465

[mail2-smtps-submission]
debug = 7
protocol = smtp
accept = 587
connect = <mail-fqdn>:587

In the logfile I have the following entries upon connecting

2018.04.30 09:20:50 LOG7[5]: Service [mail2-smtps-submission] started
2018.04.30 09:20:50 LOG7[5]: Option TCP_NODELAY set on local socket
2018.04.30 09:20:50 LOG5[5]: Service [mail2-smtps-submission] accepted connection from 41.13.8.49:56890
2018.04.30 09:20:50 LOG6[5]: s_connect: connecting 10.10.11.2:587
2018.04.30 09:20:50 LOG7[5]: s_connect: s_poll_wait 10.10.11.2:587: waiting 10 seconds
2018.04.30 09:20:50 LOG5[5]: s_connect: connected 10.10.11.2:587
2018.04.30 09:20:50 LOG5[5]: Service [mail2-smtps-submission] connected remote server from 10.10.11.11:42466
2018.04.30 09:20:50 LOG7[5]: Option TCP_NODELAY set on remote socket
2018.04.30 09:20:50 LOG7[5]: Remote descriptor (FD=23) initialized
2018.04.30 09:20:50 LOG7[5]: RFC 2487 detected
2018.04.30 09:20:50 LOG7[5]: <- 220 <mail-fqdn> ESMTP Postfix
2018.04.30 09:20:50 LOG7[5]: -> 220 <mail-fqdn> stunnel for ESMTP Postfix
2018.04.30 09:20:51 LOG7[5]: <- EHLO [100.125.153.220]
2018.04.30 09:20:51 LOG7[5]: -> 250-<mail-fqdn>
2018.04.30 09:20:51 LOG7[5]: -> 250 STARTTLS
2018.04.30 09:20:51 LOG7[5]: <- STARTTLS
2018.04.30 09:20:51 LOG7[5]: -> 220 Go ahead
2018.04.30 09:20:51 LOG6[5]: Peer certificate not required
2018.04.30 09:20:51 LOG7[5]: TLS state (accept): before/accept initialization
2018.04.30 09:20:51 LOG7[5]: SNI: no virtual services defined
2018.04.30 09:20:51 LOG7[5]: TLS state (accept): SSLv3 read client hello A
2018.04.30 09:20:51 LOG7[5]: TLS state (accept): SSLv3 write server hello A
2018.04.30 09:20:51 LOG7[5]: TLS state (accept): SSLv3 write certificate A
2018.04.30 09:20:51 LOG7[5]: TLS state (accept): SSLv3 write key exchange A
2018.04.30 09:20:51 LOG7[5]: TLS state (accept): SSLv3 write server done A
2018.04.30 09:20:51 LOG7[5]: TLS state (accept): SSLv3 flush data
2018.04.30 09:20:51 LOG7[5]: TLS state (accept): SSLv3 read client certificate A
2018.04.30 09:20:52 LOG7[5]: TLS state (accept): SSLv3 read client key exchange A
2018.04.30 09:20:52 LOG7[5]: TLS state (accept): SSLv3 read certificate verify A
2018.04.30 09:20:52 LOG7[5]: TLS state (accept): SSLv3 read finished A
2018.04.30 09:20:52 LOG7[5]: TLS state (accept): SSLv3 write change cipher spec A
2018.04.30 09:20:52 LOG7[5]: TLS state (accept): SSLv3 write finished A
2018.04.30 09:20:52 LOG7[5]: TLS state (accept): SSLv3 flush data
2018.04.30 09:20:52 LOG7[5]: New session callback
2018.04.30 09:20:52 LOG7[5]:      2 server accept(s) requested
2018.04.30 09:20:52 LOG7[5]:      2 server accept(s) succeeded
2018.04.30 09:20:52 LOG7[5]:      0 server renegotiation(s) requested
2018.04.30 09:20:52 LOG7[5]:      0 session reuse(s)
2018.04.30 09:20:52 LOG7[5]:      2 internal session cache item(s)
2018.04.30 09:20:52 LOG7[5]:      0 internal session cache fill-up(s)
2018.04.30 09:20:52 LOG7[5]:      0 internal session cache miss(es)
2018.04.30 09:20:52 LOG7[5]:      0 external session cache hit(s)
2018.04.30 09:20:52 LOG7[5]:      0 expired session(s) retrieved
2018.04.30 09:20:52 LOG6[5]: TLS accepted: new session negotiated
2018.04.30 09:20:52 LOG6[5]: No peer certificate received
2018.04.30 09:20:52 LOG6[5]: Negotiated TLSv1.2 ciphersuite ECDHE-RSA-AES128-GCM-SHA256 (128-bit encryption)
2018.04.30 09:20:52 LOG7[5]: Compression: null, expansion: null
2018.04.30 09:20:52 LOG6[5]: Read socket closed (read hangup)
2018.04.30 09:20:52 LOG7[5]: Sending close_notify alert
2018.04.30 09:20:52 LOG7[5]: TLS alert (write): warning: close notify
2018.04.30 09:20:52 LOG6[5]: SSL_shutdown successfully sent close_notify alert
2018.04.30 09:20:52 LOG6[5]: TLS fd: Connection reset by peer (104)
2018.04.30 09:20:52 LOG6[5]: TLS socket closed (SSL_read)
2018.04.30 09:20:52 LOG7[5]: Sent socket write shutdown
2018.04.30 09:20:52 LOG5[5]: Connection closed: 156 byte(s) sent to TLS, 30 byte(s) sent to socket
2018.04.30 09:20:52 LOG7[5]: Remote descriptor (FD=23) closed
2018.04.30 09:20:52 LOG7[5]: Local descriptor (FD=22) closed
2018.04.30 09:20:52 LOG7[5]: Service [mail2-smtps-submission] finished (4 left)

This is the error I am getting from K9-Mail

The google mail app just tells me:

Alpine (linux commandline smtp client)

Any advise from the gurus?

Kind regards

Ian