OK,

I have two e-mail alias tied to main .mac account (one for myself and one for my son). My wife just got a Blackberry and she is pushing all the .mac mail to it, including the alias e-mail. Is there a way so that she doesn't see the alias e-mail, but only sees the main .mac e-mail?

I hate to have to open another separate e-mail account to solve the issue. Thank you.

Set up a filter in your BIS account so that any email messages sent To: {alias address} do not get forwarded to the handheld.

(Never tried this myself, but should work in theory.)