Email from major providers arrives with a delay

Symptoms

When receiving an email from a major provider, such as Gmail, Outlook, or Yahoo, there is sometimes a delay in the message arriving in your inbox.

Description 

cPanel implements an automatic delay when new servers connect to your server to deliver mail; this is a protection to prevent spam.

Workaround

In WHM, there is an option to bypass this delay for major email providers:

1. Log into WHM
2. Navigate to "Exim Configuration Manager"
3. Enable 'Do not delay the SMTP connections for hosts in the Greylisting "Common Mail Providers" list'

Please see this article for a description of the setting mentioned above.

And see here for a related feature, Greylisting.