Log into your email and click the Settings tab (the gear in the top right corner). Select Mail at the bottom of the Settings tab.
On the left column select Accounts and then Forwarding.
Click the bubble next to Start forwarding. Enter the email address that you want to forward to.
Click Save to save the new rule.
All email received at your MBU email address will now be forwarded to the address you specified. Please note that messages forwarded by this rule will show YOU (i.e. your MBU email address) as the sender of the message, so use caution when replying to forwarded messages.