Here’s an interesting feature of Google Apps that got me into trouble recently:
The “abuse” and “postmaster” accounts are monitored by Google and always active. Even if explicitly configured in your Google Apps interface, emails to these accounts will be accepted into a Google black hole rather than bounce.
To make sure you get copies of emails going to these, be sure to create “abuse” and “postmaster” groups, otherwise you *will* miss an important email or two. Note that these need to be created as actual group addresses.. the abuse and postmaster accounts cannot be added to other addresses as an alias.