Could not resolve host

Symptoms

Your server is unable to connect outbound to another server or domain. This can happen when attempting to send mail or any time a website reaches out for remote resources. You may see an error similar to the following when connecting to a known domain:

# curl https://domain.tld
curl: (6) Could not resolve host: domain.tld

Cause

This error occurs when the server is unable to resolve hosts/domains and is typically due to the server's configured resolvers.

Resolution

Remove the current resolvers from /etc/resolv.conf and add new resolvers that can resolve remote domains. You can do this within WHM at Home / Networking Setup /
Resolver Configuration. You can view more details on this procedure here:

How to edit resolver configuration in WHM or SSH