OpenVPN on OpenVZ with Ubuntu 16.04

[Helmut Schneider]

Ken D'Ambrosio wrote:

> On 2018-07-29 15:53, Helmut Schneider wrote:
> > Hi,
> > 
> > I set up OpenVPN on Ubuntu 16.04. From the shell I can conect to all
> > services behind the VPN server:
> 
> OK.  What would be really helpful is if
> a) you tried not to use pronouns (e.g., "when it tries to forward 
> mails", I'm not sure what "it" refers to),
> b) you specified which hosts have which IPs, and
> c) said which host is trying to send e-mail where, and by what 
> mechanism.

Sure, if it helps:

- Ubuntu VM with public IP 81.169.210.199 and tun0 IP 10.0.124.18
- FreeBSD VM with tun0 IP 10.0.124.17 and em0 with IP 192.168.124.35
- Exchange Server with IP 192.168.124.249

Postfix is listening 81.169.210.199 and tries to send emails to the
Exchange server. traceroute works fine:

helmut at h2786452:~$ sudo traceroute -I exchange01
traceroute to exchange01 (192.168.124.249), 30 hops max, 60 byte packets
 1  bsdhelmut-tun0 (10.0.124.129)  19.679 ms  19.645 ms  19.739 ms
 2  exchange01 (192.168.124.249)  20.362 ms  20.303 ms  20.754 ms
helmut at h2786452:~$

> Unless you've set up firewall rules, it's much more likely either an

No firewall rules, telnet works fine:

helmut at h2786452:~$ telnet exchange01 25
Trying 192.168.124.249...
Connected to exchange01
Escape character is '^]'.
220 exchange01 Microsoft ESMTP MAIL Service ready at Mon, 30 Jul 2018
10:08:21 +0200
quit
221 2.0.0 Service closing transmission channel
Connection closed by foreign host.
helmut at h2786452:~$

> MX issue (where your mail client is pulling hosts/IPs from MX record 
> lookups), or a routing issue.

Postfix uses a transport file to find the correct MX. The Postfix log
says:

Jul 30 10:33:41 h2786452 postfix-in/smtp[31709]: 205113E0393:
to=<postmaster at mydomain.local>, relay=none, delay=30,
delays=0.02/0.03/30/0, dsn=4.4.1, status=deferred (connect to
exchange01[192.168.124.249]:25: Connection timed out)