Professor not replying to my email

Currently, I am a Master's student, and I sent an email to a professor from another department in my university. The email was about a topic which could simply be answered as yes or no. But, I have not received an answer from the Professor yet, and since I use official university email account, I have no doubt that it was not classified as spam.

It will be nearly a week, what should I do next ? Should I go directly and talk with the Professor, assuming that he did not notice my email ? Even if I was not able to arrange an appointment with him via email, should I directly knock his door, will this be considered rude ? I don't think it should be difficult to say a simple no as an answer.