Go to E-mail Settings and Edit your account.
Scroll down to Auto BCC and enter your account e-mail address.
Any sent items from your Blackberry will be automatically copied to your webmail account Inbox from where they can be dragged to your webmail sent folder. You will also get a confirmation that the email has been sent to its original recipient.
Not an ideal solution but it works well enough.
I can't comment as yet on synch'ing other folders.
Hope this helps.