For personal accounts, I recommend configuring these from your BWC webpage (Blackberry Web Client). For Rogers, it is http://www.rogers.com/bwc/
.... For T-Mobile, it is http://www.tmobile.com/bwc/
... Other carriers will have different URL's.
Don't forget that your POP accounts are not push email -- they are checked (pulled) once every 15 minutes automatically, while direct emails to Blackberry.net shows up instantly (push email). If that is preferred, you may want to setup forwards instead of a intermittent POP pull in your BWC.