Exchange 2007 Mailbox Quotas

Exchange 2007 mailbox quota plan?

Is there a rule of thumb for sizing mailbox quotas by groups? Executives=X, Directors=X, Managers=X, Staff=X, etc. And is it considered better to do this at the mailbox or have different mailbox databases for groups and set this at the database level? I've read several discussions here and there...

Exchange 2007 Storage Quotas

I have set mailbox size limits for individual users. I then set default storage limits for the database. Shortly after applying the default limits I got a call telling me that e-mail was being rejected because the receivers mailbox was full. The users mailbox was only half full. When I...