How do I add a customer to a mailbox in Help Scout?

If you are a customer service representative using Help Scout, you may need to add a customer to a mailbox in order to provide them with support. This could be necessary if the customer has contacted you through a different channel, such as email or social media, and you need to add them to the mailbox in order to respond to their query. Knowing how to add a customer to a mailbox in Help Scout is essential for providing effective customer service.