Sending emails often come with a lot of unknowns -- when you'll receive a reply, if you'll even get a reply, and if the response will be a positive one. A recent study of 300,000 messages is helping answer some of our questions. It turns out that a more casual greeting will give you a higher response rate.
Greetings like "hello" and "hey" get the best response rates, while more formal greetings like "greetings" and dear" fall lower on the spectrum. However, having a greeting is usually better than no greeting at all.
We prefer to use greetings like "hey" and "hi." They serve their purpose and set a conversational tone. "Hey" is more often used with people we know, while "hi" is mostly used with people we don't know. "Hello" isn't a bad option, but can sound a bit forced (I rarely hear people using "hello" in real life).
If you've been using "dear" and/or "greetings, try switching it up to a more conversational tone. You might just find a bump in your response rate!