In pfdavadmin, open all mailboxes. Highlight the Mailboxes at the very top level, right click propagate folder ace. Click OK at the prompt and you should get the permissions window and you will see anonymous and everyone listed, click ok. Check the two boxes
for anonymous and everyone click ok. This will add and propagate the anonymous and default to all your mailboxes
Also make a backup of the mailbox permissions before incase you screw up. Highlight mailboxes at the root and export.
James Chong MCITP | EA | EMA; MCSE | M+, S+ Security+, Project+, ITIL msexchangetips.blogspot.com