Should I mention in an email to a professor that they are referred by another one? I emails professor A about a chance to study with him, and he answers that he's on leave next academic year so not accepting new students, and I might want to check professor B. Should I mention to B that A refers her to me?

More specifically, I think that A is best suited for me. Should I be honest in saying that I have email A first? I think being honest upfront will set a better expectation from him, thus saving time for both.

Below is my intended draft:


  Dear Prof. B,
  
  To introduce myself, my name is X, from country Z. I'm writing this letter to ask you if you are planning to accept new students this year. I have asked prof A about studying with him, but he has kindly refer you to me since he's on leave next year.
  
  From reading your profile, I can see that our interests align in many aspects. My interests can be divided into two main categories, which mirror yours: 
  
  
  The cognitivism in Daoism and Buddhism's epistemology
  The physicalism in Daoism and Buddhism's metaphysics/cosmology 
  
  
  In case you are interested, here is a proposal I crafted for your reference.
  
  Do you think the program could be a good fit for me? Would there be an opportunity for me to work with you as a grad student?
  
  Best wishes and regards,


Both A and B are in the same school in Canada.
The letter is fine, but I'd actually suggest that you replace this:


  I have asked prof A about studying with him, but he has kindly refer you to me since he's on leave next year.


with something like the following:


  Prof A has referred me to you as being a good fit for my research interests. 


There is no real need for the rest of it, and might be inferred without saying it directly. 

But, your original is fine, also. Good luck.