Duplicate emails from Google/Gmail senders

Symptoms

Duplicate emails are being received from a mail server, most commonly Gmail 

Description

When the Exim feature "Introduce a delay into the SMTP transaction for unknown hosts and messages detected as spam" is enabled, this causes emails to be delivered twice, resulting in duplicate messages in the recipient's inbox.

We've opened an internal case for our development team to investigate this further. For reference, the case number is CPANEL-53742. Follow this article to receive an email notification when a solution is published in the product. 

Resolution

1. Access the WHM as the root user.

2. Navigate to Home / Service Configuration / Exim Configuration Manager.

3. Locate "Introduce a delay into the SMTP transaction for unknown hosts and messages detected as spam.” and change this from “On” to “Off”.

4. Save your settings.