CGP - Troubleshooting

NetTOOLS.ru is a nice way to detect mail problems,especially check that we are not an open relay.
Also check that our DNS settings are healthy:

$ host mail.ourdom.com
mail.ourdom.com has address 172.16.162.57
$ host 172.16.162.57
57.162.16.172.in-addr.arpa domain name pointer server.ourdom.com.

But, if you see something like

57.162.16.172.in-addr.arpa domain name pointer cl57-162-16-172.cl.yourprovider.com.

you have problems, and some SMTP servers can reject your mail with

return-path address <account@ourdom.com> rejected by mx.company.com:
550 We do not accept mail from dynamic IPs (172.16.162.57).
Please contact support@company.com

Since the in-addr.arpa domain is owed by the provider, contact them.If it is not possible, use their SMTP server as an outgoing mail gateway.

• Discover relay address:

dig +short yourprovider.com mx
10 relay.yourprovider.com

• Go to Settings/Mail/SMTP/Sending and set
  • Forward^? to: relay.yourprovider.com
• Add this relay to your SPF record in DNS:

@ IN TXT "v=spf1 ip4:172.16.162.57 a:relay.yourprovider.com -all"

• Restart DNS and verify the record

dig +short ourdom.com txt