Can it be just like this?

" Recommendation Letter

I'm writting this letter on behalf of......

______________________________

______________________________

Sincerely,

Prof. ***, M.D., Ph.D., D.M.

*********************** signature

"

or should I start it with "Dear Mr./Mrs." or "To whom it may concern:" (actually I don't understand what does this passage supposed to mean). Is it important to use this last one?

Thanks in advance!
When you say 'on behalf of' do you mean the organisation you work for? I don't think that is necessary really assuming you'll be writing on letter-headed paper. If not, I still wouldn't use 'on behalf of' just write something along the lines of 'I am the Head of the X department at X company.'

You could start Dear Sir or Madam (we don't use Mr or Mrs unless we have the person's surname).