Matt,
There are contribs that will enable you to Poll multiple POP accounts. I'm sure a forum search will find some.
I must admit that I have some clients where I do this & I don't use a contrib, what I do is this:
The email account details are in /etc/fetchmail, so you could create 2 or 3 copies of this (e.g. fetchmail.account1, fetchmail.account2 etc). Then edit each one to change the name of the Pop Server, username & password to match the additional accounts.
The fetchmail file is called from /etc/startmail (you can also force a polling of accounts by issuing the command /etc/startmail). You can edit this file so that it not only calls /etc/fetchmail, it also calls fetchmail.account1, fetchmail.account2 etc. Its a simply copy / paste of the exisiting line and then editing it to change the file name.
This will then work (for a while) and /etc/startmail will poll multiple accounts. But be warned - as soon as you make any changes to the email settings in server-manager, /ect/startmail will be recreated & your changes lost.
So you need to create a custom template for the /etc/startmail creation that includes the calls to the additional POP accounts.
All in all, probably safer to use an existing contrib, but it works for me on the odd occassion I need it and am feeling a little lazy.
Jon