There is no email god out there to tell us the one true path to follow for our electronic correspondence.
People vary. Opinions vary. Style varies.
One of the more controversial areas of email etiquette is the opening: how best to begin email messages. I grew up in the age of business letters. There was no email in business until I was safely into adulthood. That means I was extremely familiar with the traditional “Dear Ms. Smith” opening. For formal email, I still use that, and I consider it an important part of my overall email repertoire.
However, the percentage of clients who greet me with “Hi Ellen” in emails has increased dramatically in recent years. In fact, “Hi Ellen” is now by far the most common greeting I see.
There are still plenty of people who wrinkle their noses at the sight of an email “hi.” They regard it as unprofessional. Many of those people are on the older end of the workforce, although plenty of older people are also prolific “hi” users.
Starting about ten years ago, I began using “hi” plus the name in greetings, but only with clients who used it with me first.
It was scary. But I got over it, and fast.
I still don’t use “hi” with clients who favor more formal approaches with me, and by that I mean “Dear Ellen,” “Good morning, Ellen,” or just plain “Ellen.” For those clients I stick with a more formal style.
One final note: I used to place a comma between “hi” and the name, in deference to the traditional punctuation rules for direct address. In business settings I now think that can look fussy and stilted, so I have stopped. These days the only punctuation in my opening “hi” line appears after the name: “Hi Wilhelmina,” for example!
Language changes. That is not a bad thing; it is a human thing.