Auto BCC
If you need to keep an external copy of each email that your team sends to customers, consider using the Auto BCC feature.
You can enable this feature for every mailbox separately. Go to Settings > TICKETS > Mailboxes and select a desired mailbox to get started.
Add a desired email address (or multiple addresses separated by commas) to the Auto BCC field and every email sent to customers will be sent as a blind copy to that address.