If you were to ever write a Former E-mail to anyone, the tones would be "Confident" "Polite" and "Serious" Reasons:
Confident- You would want to be confident while making the email so you don't worry about the outcome. Being confident means that you are sure about your question. Polite- You would want to be polite, because 1. You would want someone to be polite to you right? And 2. because if you aren't polite to someone, they may not like you. So if you are writing a job application and not being polite (i.e using "lol" or "jk". Or saying "Give me the job" "I neeeeed the job, so give me it"), they won't hire you because you aren't polite! Serious- When writing an e-mail to anyone, you would like to be serious to get your point across. If you are saying "haha" in every sentence, they wouldn't think you are being serious and dismiss your e-mail