Setting up message archiving in SM is one way to save copies of everything coming and going, although you'd then need to search the archive every time you need to see the emails - it does not automatically create a separate email account. I use this for recovering emails that were deleted or "messed up", by users or by mailbox corruption, and find it invaluable. You could also try mightyblue.com's Ultimate Spool Manager. I am using it to copy one user's SM account to another SM account, but I believe you could use it with wildcards and copy all mail account activity to a single account. Third, you might be able to do this with a domain-wide filter in SM, but I haven't looked much into that.