Contacting POI regarding status of my application I applied for admission for a PhD at a university in the US well before the deadline. A potential advisor contacted me saying that he is recommending my application to the department. I thanked him for it. However, it has been almost one month, and I still have not received the official letter from the department. Should I send an email to the professor enquiring when I can expect the official letter?
The professor's recommendation to the department is not a promise of admission. You can ask the professor about when you might hear from the department one way or the other - particularly if you have other positions you need to decide about. You can't reasonably expect an official letter at this point.