Here you can trigger an event when the contact will have a new owner – it can be done from the contact card or by another automation rule. 

Note: This event does not start for mass assigning owners through manage contacts, or importing files from xls/csv/xlsx.

To set this rule:

[1] The type of event: contact has new main owner/co-owner.

[2] Ownership type: choose the main owner, co-owner or any of the above.

[3] Owner: choose the user’s address email.