StaffHub – Do new member StaffHub invites get sent out via email or only via text message?

StaffHub - Do new member StaffHub invites get sent out via email or only via text message?

When I send an invitation without a phone number, hoping it is going to send an email invite, nothing happens (the new member does not receive an email).  Can someone please tell me if the invite can come to the new member via email or is it limited to text message only?

Thank you!

Patty