How to sign your email to students, so to avoid their immature behavior?

Like JeffE's comment, I always prefer students to call me by my first name. My male and female, Asian and white colleagues also prefer to be called by their first name. There are some exceptions where they insist on some title according to local custom for showing respect. However, I do not have the problem you describe (students expecting unreasonable things and acting in completely unprofessional ways). The reasons that I do not have to deal with these problems is because I simply do not accept them.

Actually, I am fairly strict but also fair and I always try to be open, transparent, and predictable to my students. They know if they arrive to class late, they are absent. If they submit late, they fail. They want more time, they won't get it.

I do not see how what I allow them to call me (excluding rude names) would result in overly familiar behavior. Indeed, many of my Asian colleagues are far closer to students than I would ever allow myself to become. The ones who demand more formal forms of address are the ones who seem to get the closest with students. Perhaps this is how they remind students that they are still the teacher.

In short, student behavior is driven by your attitude towards them and you can convey a tone of seriousness in the relationship without requiring formal salutations.

Like JeffE's comment, I always prefer students to call me by my first name. My male and female, Asian and white colleagues also prefer to be called by their first name. There are some exceptions where they insist on some title according to local custom for showing respect. However, I do not have the problem you describe (students expecting unreasonable things and acting in completely unprofessional ways). The reasons that I do not have to deal with these problems is because I simply do not accept them.

Actually, I am fairly strict but also fair and I always try to be open, transparent, and predictable to my students. They know if they arrive to class late, they are absent. If they submit late, they fail. They want more time, they won't get it.

I do not see how what I allow them to call me (excluding rude names) would result in overly familiar behavior. Indeed, many of my Asian colleagues are far closer to students than I would ever allow myself to become. The ones who demand more formal forms of address are the ones who seem to get the closest with students. Perhaps this is how they remind students that they are still the teacher.

In short, student behavior is driven by your attitude towards them and you can convey a tone of seriousness in the relationship without requiring formal salutations.