What you are asking about is an addon to the paid accounts. This is also true for other competitors of Hubspot as well. The addon is called transactional emails. Basically transactional emails fall outside the scope of GDPR and CAN-SPAM because they are action based emails. For instance, you place an order at Amazon and they want to send you a confirmation. Or a service notification email is another example which is probably the closest to what you are trying to send from the sounds of it.