Politely ask a professor about my application status I have applied to PhD programs in engineering in the US. I have contacted a professor prior to applying and based on my resume he encouraged me to apply to his university. Now I want to politely ask him about the status of my application and also politely but implicitly ask him to review my application file and also maintain my contact with the professor.
The other thing is that I think that if I do not send this email, it may convey the massage that I have given up. I also want to mention that I have currently taken two other relevant courses to be more prepared before starting my program. Below I have prepared a sample email message.
I would be thankful for any help and suggestions.

Dear Professor ****,
First I want to thank you so much for your past encouragement regarding the next step in my academic development. I am very excited about having the opportunity to apply to the university of **** and having this honor to mention your name in my application form. I would be more than grateful if you could please let me know when I might hope to hear any response from **** regarding my application. I would also like to mention that I am taking the two **** and *** courses to be more prepared before starting my program.
Again, thank you very much for all your kind consideration.
I think that's too formal, you want to use a more informal communications channel such as email and just say "just wanted to ask if you know the status of my application" period.   That gives him the option of gracefully declining to answer.  You do not know what internal politics are going on in the program and what they are going to do with your application and there's really no way of forcing them to do anything.  All you really need to do is confirm that they got it.  Hopefully you are also aware that you should be looking at other programs and not setting your heart on just this one.

The other benefit of using an informal approach is that you can repeat it without appearing to be obnoxious.  Send him an email now, then keep doing it every couple weeks.  Sending a big old formal letter is kind of demanding a formal decision and response and puts them on the spot, and if you keep sending such letters then you come across as rigid and demanding.  Whereas an informal one-liner email isn't going to be perceived as demanding (it might be perceived as begging, but that's OK)