Some users' are quite itchy with their hands and they will accidentally delete away their INBOX folder.
If you recover the inbox folder from the mail template, you discover that all entries are gone! You may ask yourself with a sigh, "Do I really have to go through the hassle of recovering the mail file from backup?"
Here's a solution without having to go through all those troubles...
(1) Firstly, copy the INBOX folder design element back to the mail file.
(2) Open up the hidden view ($Sent) and copy its first column formula i.e... @If(DeliveredDate=""; @If(PostedDate="" | @IsUnavailable(PostedDate); 58; @If(Importance="1";124;122)); 0)
(3) Open up the hidden view ($All) and paste the copied formula into the view selection and make a negation of it (this will filter off all posted documents) i.e... SELECT !@If(DeliveredDate=""; @If(PostedDate="" | @IsUnavailable(PostedDate); 58; @If(Importance="1";124;122)); 0)
(4) Go to the "All Documents" view and drag all the documents into the new Inbox folder.
(5) Finally, set back the view selection formula for ($All) view i.e... SELECT @All