Client Identification

I have two seperate clients (using fetchmail) on two seperate machines that use the same login and the same ip address as each other fetching their mail over IMAP using IMAP idle. Naturally Dovecot assumes that they are the same machine but they are not so messages only get downloaded to one of the machines rather than both which is what I want. How do I get Dovecot to recognize them as two individual clients so that mail downloads to both of them?

Regards, spaceman