I often set up peoples’ computers to fetch their GoogleMail from multiple computers (eg: home and work). They don’t want their home PC to remove the email from the server so that their work PC doesn’t see the emails any more. I found this post describing what to do: Using POP on multiple clients or mobile devices
Gmail's 'recent mode' makes sure that all messages are made available to each client, rather than only to the first client to access new mail.
Recent mode fetches the last 30 days of mail, regardless of whether it's been sent to another POP client already.
Setting up 'recent mode':
In your POP client settings (ie: in your email program on your PC), replace 'firstname.lastname@example.org' in the 'Username' or 'Email' field with 'recent:email@example.com' (leave out the 's)