SOLVED Possible rDNS issue

monkey64

Well-Known Member
Nov 6, 2011
121
5
68
cPanel Access Level
Root Administrator
I'm experiencing issues sending emails to, in particular, gmx addresses. The error received indicates a bad PTR record:

Code:
Action: failed
Final-Recipient: rfc822;[email protected]
Status: 5.0.0
Remote-MTA: dns; mx00.emig.gmx.net
Diagnostic-Code: smtp; 554-gmx.net (mxgmx015) Nemesis ESMTP Service not available
554-No SMTP service
554-Bad DNS PTR resource record.
554 For explanation visit https://www.gmx.net/mail/senderguidelines?ip=12.34.56.91&c=rdns
I checked out the URL in the error and everything looked fine until I ran a HELO test and the error received was:

Code:
550 *** The HELO for IP address 12.34.56.91 was 'server-91.myserver.com' (valid syntax) ***
Reporting-MTA: dns; server-215.myserver.com
The domain I'm sending from has a dedicated IP 12.34.56.215 and the main server address is 12.34.56.91. The domain has valid DKIM, SPF records etc and we experience no other sending issues. If I look at the 'Email Deliverability' section in the user's cPanel, there is a blue warning which says:

Code:
The system uses an alternate HELO of “server-91.myserver.com” when sending mail from the “mydomain.co.uk” domain.
I did try setting the 'Send mail from the account’s IP address' in the Exim Configuration Manager to 'Off' and rebuilding the RDNS cache but I still received bounces. I'm not sure what I need to do to fix this other than removing the dedicated IP entirely and sending everything from the server IP.

Can anyone help me please?

Thanks
 

ankeshanand

Well-Known Member
Mar 29, 2021
195
59
103
India
cPanel Access Level
Root Administrator
What is the rDNS Record on the Dedicated IP(Sending IP)? Point the Dedicated IP rDNS to the Domain Assigned. Could you also check if the Domain DNS has SPF and DKIM valid records...
 

monkey64

Well-Known Member
Nov 6, 2011
121
5
68
cPanel Access Level
Root Administrator
Although dig showed that the rDNS pointed to the correct domain name, I don't think the change had fully propogated. Shortly after writing this post everything started working. Typical :)

Code:
dig -x 12.34.56.78 +short