Hi Chippy,
The issue you are experiencing is a very common issue that is "normally" resolved by deleting the email account from the BIS web client and then recreating it after 10 minutes (This to allow time for the device to receive the configuration changes). In some circumstances I have had to log onto the users BigPond account and set an email forward rule to forward all items to the users BIS email address (e.g.
user@telstra.ap.blackberry.net) to correct the issue (or technically to work around the issue).
Thanks,
Gary