1. Do not use all caps.
Using all caps is rude and considered online screaming.
2. Do not reply to spam.
People who are spamming you are looking for a reaction don't respond.
3. Answer quickly.
People do not like waiting for a reply.
4. Do mot make emails long.
Summarize your email. People will be discouraged to read long emails.
5. Do not use email to discuss secrets.
People can access your accounts and even the goverment looks at your stuff.