We own a domain name (e.g. externaldomain.com) and currently have an e-mail address associated which simply forwards to one of our staff. There is now a need for this to become a mailbox and the ability to reply to e-mail as the e-mail address (and not as our internal e-mail address).
Is this a case of adding the external domain to our DNS somewhere, or associating it with our internal domain so that it becomes available as an e-mail address i.e. firstname.lastname@example.org which can be added to a shared mailbox?
How is this done, please?