I use Google Apps as my server, which collects into "Sent Items" any email I sent from the POP client (and makes them available over IMAP should I need them).

I use Google Apps as my server, which collects into "Sent Items" any email I sent from the POP client (and makes them available over IMAP should I need them). For mail sent from my IMAP clients, I use "automatically BCC myself" thus ensuring a copy ends up at the POP client.