PTR, reverse DNS records for dedicated server

[Matt]

If they don't bounce the problem is probably on the recipient mailserver. You should always receive a bounce if the problem is on your end.

Did you check your spam folder(s) to see if the bounce was in there? If its not there, then the best thing to do is to send another email, verify it did not make it, then open a support ticket with the sender and recipient address so we can have a look at the logs.

Make sure you do not wait too long after sending the email / opening a new ticket otherwise the logs we look at may be too old and won't contain the information that we need to troubleshoot the problem.