So I'm having a bit of an issue here that is extremely important to fix as I consider my BlackBerry as a mobile workstation.
I have BIS and I'm using a 9700 with OS6.
Recently, I switched jobs. At my previous one, we used Google Apps and whenever I sent an email on my desktop, it would show on my BlackBerry as well. Same thing when I sent from my Blackberry; it would show up in Google Apps webmail.
Now, I'm at a company that uses its own thing, not Exchange and I have access to my email throw POP3 but the things I send on my workstation don't show up on my phone and the things I send from my phone dont show up in my desktop's Outlook.
only way to get around that is to set up a second email address and send a BCC to it and have it go to your BB. Similar thing with another address from the BB. The limiation is with the POP3 service.
I've never looked into it especially thoroughly, but does BB's "Reconcile" feature not address the OP's question/need? I've never used it, so maybe it doesn't do that but I thought I'd at least mention it.
As has been said the only way to do it is add a BCC. This can be done automatically within the email setup.
You can BCC your own address and set up a filter not to deliver them to your BB or you can set up a secondary address that doesn't deliver to your BB and set that address up as the BCC and then reconcile them into the sent items when you are using Outlook.