I could not find this information anywhere on the web (perhaps I did not look hard enough!) but the file attached to this post is a full audit of the default security and mailbox permissions for an Exchange mailbox (well when I say default, it’s not quite the default permissions - they have been slightly modfied to suit my environment - but if you are in a pickle with a mailbox and you think that it is permissions based then this is a good place to start making some comparisons)- might prove useful.

The audit is located here: http://www.telnetport25.com/legacySites/msex/Exchange-Permissions-Account.xls