I had already written a simillar script, that would go thru an entire Cluster and SGs, these one implements same theory but it is more flexible and easy to use.
Basically you will get 3 types of info and all easily imported to excel, so you can show your boss a nice report.
Detailed information of each mailbox:
Servername; SG; DB; MailboxName; Size(Kbytes); Total Emails
SERVERMAIL;’First Storage Group’;’VIPS’;78
SERVERMAIL;’First Storage Group’;’USERS’;201
Basically I built a sub that can be called like this: