You need a forwarding email address when you have a domain name. All email addresses that use the domain name will be forwarded to a "real" (destination) email address.
email@example.com - forwards to -> firstname.lastname@example.org
email@example.com - forwards to -> firstname.lastname@example.org [must be a pop email account]
NOTE: For this second example to work email@example.com would need to be set up as a pop mailbox. It cannot be yet another fowarding rule.
If you are transferring your domain name you will need to provide us with a "real" (destination) email address so we have somewhere to forward your domain name email to.
If you don't have an alternative email address, then we can set you up a new POP3 mail account.