From last couple of days cpanel / webmail users are getting duplicate emails issue. Emails coming from gmail are duplicating, sometime same email is even coming by 3, 4 time. Each email comes with a difference of 10 to 15 seconds etc
Reason, actually there is a bug with gmail servers where their email retry time is decreased to that low as 10 seconds. Standard WHM (cPanel) servers are configured to check every incoming message to see if it is a spam or not for that purpose cpanel servers usually delay the messages for few seconds before delivering it to final recipient, meanwhile gmail servers detects that their email is not delivered or blocked so they send their same email again with a different IP address to bypass recipient servers and on the other hand cpanel servers approves the first incoming message then it receives the next one after 10 seconds there for customers receive duplicate emails.
Solution:
Temporary solution is to disable that delay on whm servers side to avoid that duplication, and wait for the fix from gmail side.
Follow these steps to disable that delay:
1. Login ti WHM server as roor user
2. Navigate to Exim Configuration Manager
3. Location option (Introduce a delay into the SMTP transaction for unknown hosts and messages detected as spam)
4. Turn this option from ON to OFF
5. Save your settings.