Hello,

A company which we work with wants to send secure (TLS) mails to our server. I think stunnel can do the trick for me, as our own server (Scalix) doesn't support TLS for itself. Now I set up stunnel and it looks like its working, except it's not receiving secured mails. I can still receive normal mails, so somehow it is not working.

I used the sample config and filled in the things I thought I needed. My config:

; Sample stunnel configuration file for Unix by Michal Trojnara 2002-2015 ; Some options used here may be inadequate for your particular configuration ; This sample file does *not* represent stunnel.conf defaults ; Please consult the manual for detailed description of available options

; ************************************************************************** ; * Global options * ; **************************************************************************

; A copy of some devices and system files is needed within the chroot jail ; Chroot conflicts with configuration file reload and many other features ; Remember also to update the logrotate configuration. ;chroot = /usr/local/var/lib/stunnel/ ; Chroot jail can be escaped if setuid option is not used ;setuid = nobody ;setgid = nogroup

; PID file is created inside the chroot jail (if enabled) ;pid = /usr/local/var/run/stunnel.pid

; Debugging stuff (may be useful for troubleshooting) debug = 7 output = stunnel.log

; ************************************************************************** ; * Service defaults may also be specified in individual service sections * ; **************************************************************************

client = no ; Certificate/key is needed in server mode and optional in client mode cert = /usr/local/etc/stunnel/stunnel.pem ;key = /usr/local/etc/stunnel/mail.pem

; Authentication stuff needs to be configured to prevent MITM attacks ; It is not enabled by default! ;verify = 2 ; Don't forget to c_rehash CApath ; CApath is located inside chroot jail ;CApath = /certs ; It's often easier to use CAfile ;CAfile = /usr/local/etc/stunnel/certs.pem ; Don't forget to c_rehash CRLpath ; CRLpath is located inside chroot jail ;CRLpath = /crls ; Alternatively CRLfile can be used ;CRLfile = /usr/local/etc/stunnel/crls.pem ;sslVersion = all ; Enable support for the insecure SSLv2 protocol ;options = NO_SSLv2 ; Enable support for the insecure SSLv3 protocol ;options = NO_SSLv3 ; Workaround for Eudora bug ; options = DONT_INSERT_EMPTY_FRAGMENTS

; These options provide additional security at some performance degradation ;options = SINGLE_ECDH_USE ;options = SINGLE_DH_USE

; ************************************************************************** ; * Service definitions (remove all services for inetd mode) * ; **************************************************************************

; Example SSL server mode services

;[pop3s] ;accept = 995 ;connect = 110

;[imaps] ;accept = 993 ;connect = 143

[ssmtp] accept = 192.168.1.102:25 connect = 192.168.1.102:26 protocol = smtp

; Example SSL client mode services

;[gmail-pop3] ;client = yes ;accept = 127.0.0.1:110 ;connect = pop.gmail.com:995

;[gmail-imap] ;client = yes ;accept = 127.0.0.1:143 ;connect = imap.gmail.com:993

;[gmail-smtp] ;client = yes ;accept = 127.0.0.1:25 ;connect = smtp.gmail.com:465

; Example SSL front-end to a web server

;[https] ;accept = 443 ;connect = 80 ; "TIMEOUTclose = 0" is a workaround for a design flaw in Microsoft SSL ; Microsoft implementations do not use SSL close-notify alert and thus ; they are vulnerable to truncation attacks ;TIMEOUTclose = 0

; vim:ft=dosini

This is what I see in the logfiles for the mails I don't receive:

2015.03.21 14:56:46 LOG7[main]: Service [ssmtp] accepted (FD=12) from 207.46.163.207:8478 2015.03.21 14:56:46 LOG7[2]: <- EHLO na01-by2-obe.outbound.protection.outlook.com 2015.03.21 14:56:46 LOG7[2]: -> 250-mailserver.mydomain.nl 2015.03.21 14:56:46 LOG7[2]: -> 250 STARTTLS 2015.03.21 14:56:46 LOG7[1]: SSL state (accept): SSLv3 read client key exchange A 2015.03.21 14:56:46 LOG7[1]: SSL state (accept): SSLv3 read finished A 2015.03.21 14:56:46 LOG7[1]: SSL state (accept): SSLv3 write change cipher spec A 2015.03.21 14:56:46 LOG7[1]: SSL state (accept): SSLv3 write finished A 2015.03.21 14:56:46 LOG7[1]: SSL state (accept): SSLv3 flush data 2015.03.21 14:56:46 LOG7[1]: 1 items in the session cache 2015.03.21 14:56:46 LOG7[1]: 0 client connects (SSL_connect()) 2015.03.21 14:56:46 LOG7[1]: 0 client connects that finished 2015.03.21 14:56:46 LOG7[1]: 0 client renegotiations requested 2015.03.21 14:56:46 LOG7[1]: 1 server connects (SSL_accept()) 2015.03.21 14:56:46 LOG7[1]: 1 server connects that finished 2015.03.21 14:56:46 LOG7[1]: 0 server renegotiations requested 2015.03.21 14:56:46 LOG7[1]: 0 session cache hits 2015.03.21 14:56:46 LOG7[1]: 0 external session cache hits 2015.03.21 14:56:46 LOG7[1]: 0 session cache misses 2015.03.21 14:56:46 LOG7[1]: 0 session cache timeouts 2015.03.21 14:56:46 LOG6[1]: No peer certificate received 2015.03.21 14:56:46 LOG6[1]: SSL accepted: new session negotiated 2015.03.21 14:56:46 LOG6[1]: Negotiated TLSv1 ciphersuite AES256-SHA (256-bit encryption) 2015.03.21 14:56:46 LOG7[1]: Compression: null, expansion: null 2015.03.21 14:56:46 LOG7[3]: Service [ssmtp] started 2015.03.21 14:56:46 LOG5[3]: Service [ssmtp] accepted connection from 207.46.163.207:8478 2015.03.21 14:56:46 LOG6[3]: s_connect: connecting 192.168.1.102:26 2015.03.21 14:56:46 LOG7[3]: s_connect: s_poll_wait 192.168.1.102:26: waiting 10 seconds 2015.03.21 14:56:46 LOG5[3]: s_connect: connected 192.168.1.102:26 2015.03.21 14:56:46 LOG5[3]: Service [ssmtp] connected remote server from 192.168.1.102:22148 2015.03.21 14:56:46 LOG7[3]: Remote socket (FD=13) initialized 2015.03.21 14:56:46 LOG6[1]: Read socket closed (readsocket) 2015.03.21 14:56:46 LOG7[1]: Sending close_notify alert 2015.03.21 14:56:46 LOG7[1]: SSL alert (write): warning: close notify 2015.03.21 14:56:46 LOG6[1]: SSL_shutdown successfully sent close_notify alert 2015.03.21 14:56:46 LOG7[2]: <- STARTTLS 2015.03.21 14:56:46 LOG7[2]: -> 220 Go ahead 2015.03.21 14:56:46 LOG7[2]: SSL state (accept): before/accept initialization 2015.03.21 14:56:46 LOG7[3]: RFC 2487 detected 2015.03.21 14:56:46 LOG7[3]: <- 220 mailserver.rsconsultancy.nl ESMTP Scalix SMTP Relay 11.4.6.13676; Sat, 21 Mar 2015 14:56:46 +0100 (CET) 2015.03.21 14:56:46 LOG7[3]: -> 220 mailserver.rsconsultancy.nl stunnel for ESMTP Scalix SMTP Relay 11.4.6.13676; Sat, 21 Mar 2015 14:56:46 2015.03.21 14:56:46 LOG6[1]: SSL socket closed (SSL_read) 2015.03.21 14:56:46 LOG7[1]: Sent socket write shutdown 2015.03.21 14:56:46 LOG5[1]: Connection closed: 52 byte(s) sent to SSL, 6 byte(s) sent to socket 2015.03.21 14:56:46 LOG7[1]: Remote socket (FD=9) closed 2015.03.21 14:56:46 LOG7[1]: Local socket (FD=3) closed 2015.03.21 14:56:46 LOG7[1]: Service [ssmtp] finished (2 left)

Could anyone please tell me what I'm doing wrong?

Jeroen