Unable to Connect to SMTP Host

I am trying to configure Postfix on CentOS 6 server, and the problem is that I cannot receive mails.
I tested it on http://mxtoolbox.com/ and I get an error Unable to Connect to SMTP Host.

I check with netstat -tulpn | grep :25 and I see that postfix seems to be listening to port 25 just fine.

I disabled Selinux (and rebooted) – it doesn't solve the problem.

My server is on OVH (if it matters. may be OVH have some firewall) And I reinstalled CentOS just now.
It's possible to see my /etc/postfix/main.cf file here, if you whant.
What should I do next to resolve this problem? And how can I debug SMTP connection problems?

Any help will be appreciated!

iptables output:

[root@jewishonline log]# iptables -L -v
Chain INPUT (policy ACCEPT 1590 packets, 285K bytes)
 pkts bytes target     prot opt in     out     source               destination

Chain FORWARD (policy ACCEPT 0 packets, 0 bytes)
 pkts bytes target     prot opt in     out     source               destination

Chain OUTPUT (policy ACCEPT 2264 packets, 627K bytes)
 pkts bytes target     prot opt in     out     source               destination

port 25:

[root@jewishonline log]# netstat -ntlp | grep 25
tcp        0      0 127.0.0.1:25                0.0.0.0:*                   LISTEN      2756/master