Mark, you are partially correct but the user's, even those without BES have much more choice:
Run the Blackberry redirector. If you have a computer at home or work that is always turned on, you could theoretically use the Blackberry Redirector to redirect Work (or other) e-mail account, while you use the web client for another.
When composing an e-mail i have the same selection mark has.
How I do it:
a) I use my blackberry.net account for my home e-mail accounts. I forward all mail, at the server, direct to this account. This way mail is delivered instantly. IF you choose to check mail on your web client through the web mail interface, you will only get mail every 15 minutes or more.
b) I use my blackberry redirector at work, which connects to Microsoft Outlook. You do not need Exchange, and the Redirector does work with other mail clients. You must leave the computer on at all times in order for e-mail to be delivered however..
How does it work:
a) For my home account, i get all my mail through the web client. When i reply to a message that came from web-client it is AUTOMATICALLY sent through web client. Your message will come from
with a REPLY-TO address set to your address which you must place into your web client. Therefore users will know you are on the blackberry, but at least it works..
b) For work, as above when you reply from your redirector account all messages are automatically sent through the redirector.
c) When i compose a new message you can select which account you are using, therefore selecting the e-mail address you are going to be shown as.
a) If you have a laptop, you will not be able to use the redirector as it needs to be always on. Maybe you'll set up your own 'server' for the redirector.. why not?
b) Your internet service must be always on and reliable.
c) Your computer must have reliable power and it can't be shut off on a regular basis!
That's about it.. good luck.