Sounds like your company set the IT Policy to not allow other email accounts. That means you can receive email, but it all goes out from your work address. They do this to prevent people from forwarding work-sensitive emails to others via an unsecured email account. If it's forced out thru your work email account, there are audit trails.
If that's the case, there isn't anything you can do. You can ask the BES Admin, but I doubt they will budge.
No longer a BES Admin, but it was fun while it lasted!