You may arrange with your ISP that all email for your domain come into a single account. WinRoute may check such an account, pick up the messages and automatically distribute them into the mailboxes of local users.
Example
Your ISP arranged mailbox company@mail.isp.net. You may have domain company.com but all email for your domain (sales@domain.com, john@domain.com) comes to the mailbox company@mail.isp.net at ISP.