See this guide on activating auto emails for screenshots of what steps to take.
After logging into Matrix, click the My Matrix tab, then the Auto Emails link. Locate the auto email you want to edit. Click the triangle next to the auto email to display options. (If you have a large number of auto emails, you can make your search easier by filtering them with the Choose a filter drop-down menu.) Click Criteria to update your Saved Search criteria. Review and modify the search criteria used to generate the auto email; when finished, click Save.
Verify that the Contact selected in the drop-down list is correct, as well as the CC: field. If desired, check the box to BCC me a copy of all emails. Then, edit the email Subject and Message if desired, and click on Enabled to enable the auto email. Click Save to complete.
(Note: if your auto email returns more than 250 listings, the email will be disabled. To re-enable, narrow your search criteria and re-activate the auto email. If necessary, you can set up multiple saved searches for a single client.)