- The Email Deliverability interface will report that Reverse DNS or PTR records are invalid despite the fact that they are valid and setup properly.
- IPv6 addresses are configured on the server:
# ip a | grep inet6But pinging an IPv6 address is not possible:
inet6 ::1/128 scope host
inet6 fe80::8edc:d4ff:fea9:9f54/64 scope link
# ping6 google.com
connect: Network is unreachable
The Email Deliverability interface will default to using IPv6 when checking PTR records if IPv6 is enabled.
When IPv6 is enabled but broken, the Email Deliverability Interface will incorrectly attempt to validate the PTR record via IPv6, which fails.
cPanel has a mechanism for detecting this situation to prevent the problem from happening, but the detection is not currently working correctly. You can read more about this by reading and following the case article.
Issue the following command via SSH or Terminal as the root user:
Then check the Email Deliverability page.