You have several mail forwarders available, the exact number depends
on your account. Mail forwarding enables you to have email addressed
to specific people at your domain to be forwarded to another email
address elsewhere, or to a POP/IMAP account you have created. (Examples:
email@example.com forwards to firstname.lastname@example.org, email@example.com
forwards to your sales POP account)
By default, ALL mail to your domain is set up to automatically
forward to the e-mail address that you supplied when you purchased
your account. This e-mail address is called the "default" address.
Any mail sent to your domain that does not fit any of the additional
forwarding options you have set up will be sent to this address.
Example: You have setup firstname.lastname@example.org, and someone sends
email to email@example.com, the sales email will be sent to the
"default" address since sales was not explicitly setup.
If this behaviour is undesired, simply delete the "default" alias.
All of this can be configured with your account