You may use the following procedure for testing Callback / Callout Verifications.
- Access the command line on the destination server as the 'root' user via SSH or the "Terminal" application in WHM.
- Find the MX server of the domain for the address that you are testing with the following command:
dig +short domain.tld MX
- Use telnet to connect to the MX server on port 25:
telnet mx1.domain.tld 25
- Issue the following commands:
If the remote server responds with a
250 Accepted response, it means that the callback verification succeeded and the email address does exist on the server.