CGP - Troubleshooting< 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 has address
$ host domain name pointer<

But, if you see something like domain name pointer<

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

return-path address <[email protected]> rejected by
550 We do not accept mail from dynamic IPs (
Please contact [email protected]<

Since the 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 mx
  • Go to Settings/Mail/SMTP/Sending and set
    • Forward? to:
  • Add this relay to your SPF record in DNS:
@ IN TXT "v=spf1 ip4: -all"<
  • Restart DNS and verify the record
dig +short txt