Sending Email is very slow or fails/times out

Symptoms

When trying to send an email using webmail the email send is very slow and potentially errors after time.

Description

This is often due to slow DNS resolver servers taking an extended amount of time to locate the servers they are sending mail to.

Workaround

The best approach is to contact your server/service provider and ask what DNS servers are available in the data center used to host the server. If this is not possible or may take too long then you can use publicly available DNS servers.

1. Access WHM as the root user
2. Navigate to Home / Networking Setup / Resolver Configuration
3. Click Proceed to start the wizard and enter the new set of resolvers into the prompt.
4. Complete the wizard to commit the changes.

The two most common public resolvers are the Google DNS servers and Cisco OpenDNS servers: