I will try and make this as simple as possible.
I'm a wedding photographer and have a website and email attached to the domain name.
my email is will say
this would be your regular email account you use at home to send and receive email.
At the server level I have two email accounts the main account and a copy account.
My blackberry is setup so that when I send email is has the FROM address to show as Main
When I send an email from my blackberry I have it setup with nextel for a Auto BCC: to my copyaccount.
So any email conversion I have with someone, when I get home I open outlook and all my Set email from my BB are filtered to my sent mail.