It's really fishy.  Who has a header that has "(omitted)" for phone and fax?  Wouldn't they just like not put it there? What doctor would send it on stationary linked to his practice? Why would it have hand written Personal & Confidential...on the back of the envelope?  Maybe personal but there is no confidential information.  Not all doctors are genius wordsmiths, but the childish writing makes me think it is fake.