What't the difference between "Please be advised" & "please advise"

1. Please be advised that we have received your letter. This means 'We want to tell you that we have received it'. It's a standard business expression. Personally, I dislike this as it seems to serve no purpose usually. I'd omit it, and just say 'We have received your letter.
 
2. Please advise that we have received your letter. This is wrong. It makes no sense.