0

Our e-mails mostly get through fine, but here's an error I haven't seen before.

Diagnostic-Code: smtp;550 5.7.1 ... Forged hostname for 66.132.221.45 >which resolves as www.medialabinc.net but www.medialabinc.net does not resolve back to >66.132.221.45. Check your DNS A and PTR records.

We have PTR records for our two server's IPs (the IPs that send mail, 66.132.221.45 and 66.132.221.46). medialabinc.net resolves to 66.132.220.196, which is the IP of the load-balancer. So, we have:

PTR

66.132.221.45 => medialabinc.net

66.132.221.46 => medialabinc.net

A

medialabinc.net => 66.132.220.196

Is there anything I can do here, if wayne.edu is insisting that 66.132.221.45 => medialabinc.net => 66.132.221.45?

Tim Westover
  • 133
  • 3

1 Answers1

0

The target mailserver rejects this message because your outbound IP's don't pass FcRDNS checks. your outbound mail IP shouldn't use a PTR which points to a completely different IP ( www.medialabinc.net -> 66.132.220.196). you could give each outbound IP a unique PTR which resolves back to the IP and you're all set.

Example:

  • 66.132.221.45 PTR outbound1.medialabinc.net
  • outbound1.medialabinc.net A 66.132.221.45
  • 66.132.221.46 PTR outbound2.medialabinc.net
  • outbound2.medialabinc.net A 66.132.221.46
Gryphius
  • 2,720
  • 1
  • 19
  • 19