Introduction
When IPv6 is disabled for Exim, no IPv6 activities take place. AAAA records are never looked up, and any IPv6 addresses that are listed in local_interfaces, data for the manualroute router, etc. are ignored. If IP literals are enabled, the ipliteral router declines to handle IPv6 literal addresses.
Procedure
1. Navigate to the Exim configuration Manager (WHM > Service Configuration > Exim configuration Manager)
2. Click on Advanced Editor
3. Scroll down to where you can click the button that says "Add additional configuration setting" (it's just above Section: BEGINACL")
4. Select disable_ipv6 and type true in the box next to it:
5. Save