There are different types of communication you can take to communicate with the tenant

1) Sending an email directly: tenant will always receive an email. There is NO flag to turn it on or off

From the tenant details page:

2) Send Portal Message/Email via message feature: tenant will always receive the message. There is NO flag to turn it on or off. The tenant will also receive this message in the tenant portal.

Follow this article for more information: Send an email directly