When you send emails from Matrix, email recipients will have the option to unsubscribe from Matrix emails. If your client clicks the link the "unsubscribe" link at the bottom of an email sent from Matrix, it will disable their auto email search.  There are two steps to re-enable their auto email:

1.    Your client must send a blank email to [email protected] from the email address they used when they unsubscribed.
**Absolutely nothing should be written in the body of the email.**
 
2.    You must go to My Matrix, choose "Auto Emails". Click on the name of the auto email (under Subject column) or the corresponding downward-pointing arrow to open the full options; then click "Settings".

3.    On the settings screen, under your message, change the auto email to "Enabled" and click save.
Your client should now be able to receive emails from Matrix.