I currently have masters degree in an engineering field and I am currently not having any PhD degrees (I may study for a doctorate degree in future). It happens that when I go to conferences or scientific occasions, even in the emails I receive from people; they use a doctor prefix for my name; but I am not holding a PhD degree.

What is a good etiquette to deal with such thing? Should I directly tell them that I am not holding a doctorate degree? Or should I neglect such mistake by them and don't do anything?

I think it is unethical not to correct such thing, because the person may still think that I am holding a PhD degree; and such wrong usage of title should be corrected some way. Once a person used doctor title for my name in an email and I just added a line in my reply to his email, stating that I have a masters degree.