Using a separate outgoing email without downloading the full delegate mailbox, Outlook 2011?

In the organisation I work for I have my own personal mailbox, and there is a group email for the department. For outgoing emails to customers I need to use this group email as my sender address, while internal emails can come from my personal address.

I have achieved this by adding the group mailbox as an account I can delegate for. This works.

Problem is, it's now going ahead and downloading each and every email & attachment archived in the group mailbox onto my machine. This is a pointless use of space.

Is there a different way I can do this? Or can I stop it from downloading emails from this specific mailbox automatically, while it should still download for my personal one?

Has anyone worked with this?

Thanks