In an e-mail, suppose we start with Hi John. Should I follow with
Hi John, some content (i)
some content (ii)
Is there any etiquette behind choice (i) vs (ii)?
You should use two new lines, so that there is a blank line between the “Hi John,” and the beginning of the email text. Similarly, you should use two new lines before your salutation. For example:
Thanks for coming to the meeting. Could you send me the
slides you mentioned by the end of the day?
It’s not an etiquette thing. Some people don’t format their emails like this, but that’s done primarily out of laziness rather than rudeness in my experience.
By the way, you can use the code environment on this page to ignore the website’s formatting rules. I’ve edited it into your post.