Use Reverse DNS as HELO/EHLO

HELO and EHLO are commands sent by an email server to identify itself when connecting to another email server to send an email. In some cases, the HELO may not match the the PTR, or reverse DNS, record for the sending IP address.
Some mail servers may reject your emails if these values do not match. You may also see an error like the following on the Email Deliverability page in cPanel:

The system uses an alternate HELO of “oldPTR.domain.com” 
when sending mail from the “server.domain.com” domain.

Here we cover the steps to configure your server to use the reverse DNS entry for the mail HELO.

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Use Reverse DNS as HELO

IMPORTANT: This solution will require root access. If this needs to be obtained, follow the guide on requesting root access.

1. Log into Root WHM
2. Expand the Service Configuration dropdown and select Exim Configuration Manager
   
3. On the Domains and IPs tab change the radio button beside Use the reverse DNS entry for the mail HELO/EHLO if available from Off to On
   
   
4. Click the Save button