1. ASAP. You should try to respond as quickly as possible don’t take weeks to respond
2. This shows and makes the people think you cannot write or type well. It can also mean an angry tone and this may not sit well with them
3. It is to put something that will notify the person receiving the email of what to expect in it something that makes them open it
4. You could however be cautious as some places or business can track or even read them without your consent as a random check
5. Your should have a very proper tone, You can do this by having proper punctuation and overall a strong email that get the message across.
6. Your should make sure that you have all you want to say in the email and make sure you proof read to make sure there is proper punctuation and overall make sure the email is as perfect and professional it can be.
Hope this helps :)