Many times, it happens that sending emails to Gmail or few other ISP’s are getting rejected when Ipv6 networking is enabled on the server.
This is basically because, exim attempts to deliver the emails using IPv6 network by default and some times it returns the message “Network is unreachable“, specially to Gmail addresses.
This can be easily fixed by forcing exim to deliver the emails using the IPv4 IP address instead of IPv6 address.
You can follow below simple steps to disable IPv6 in exim ::
Login to "WHM Home » Service Configuration » Exim Configuration Manager » Advanced Editor"
Scroll down until you see “Add additional configuration setting” (it’s just above Section: BEGINACL“).
Then, select the following option from the drop-down menu:
and set the value to true:
disable_ipv6 = true
then scroll to the very bottom of the page, and click “Save”.