How to perform a test Callout / Callback  Verification

Introduction

You may use the following procedure for testing Callback / Callout Verifications.

Procedure

1. Access the command line on the destination server as the 'root' user via SSH or the "Terminal" application in WHM.
2. Find the MX server of the domain for the address that you are testing with the following command:

   dig +short domain.tld MX

3. Use telnet to connect to the MX server on port 25:

   telnet mx1.domain.tld 25

4. Issue the following commands:

   HELO any.hostname.tld

   MAIL FROM:<>

   RCPT TO:<sender@domain.tld>

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.

Additional resources

What is the difference between "Sender Verification" and "Sender Verification Callouts" in the Exim Configuration Manager?