Ful text index with Encrypted Mail

Dear Expert

I dont understant why I cant search any words in my Mail Body field if the email is encrypted.

I saw in Domino Admin Help have statement :

“Index encrypted fields:Searches all words in fields, including encrypted fields”

and from LNotes, it just encrypt body field. and base on the above statement it’s will search all word included encrypted mail.

But here I cant search, why have any idea ???

thks