Email

It is polite to use a subject so your receiver knows what the email is about. It is also polite to be formal since emailing is a more formal setting than texting. Address your receiver and if you are asking for something, remember to say thank you in advance.

It is rude to be informal, treating the email like a text and abbreviating words. It is wise to avoid using slang terms and obscenities. It is also rude to send a meaningless email with as few words as possible; make it meaningful, showing the receiver that you care about your email and it's message.