You can configure automated emails to be sent whenever certain actions take place in your board. Currently, you can send an email for the following two cases:
To configure these settings, simply open your board 'Settings' and navigate to the 'Details' tab as shown below. Enable the 'Send Email on Status Change' setting if you'd like the board to send an automated email to the card's assigned users whenever the status of the card is changed. Enable the 'Send Email on Card Update' setting if you'd like the board to send an automated email to the card's assigned users whenever the card details/fields are updated.