If I'm sending it to one person I'll open with "First," or "Hey/Hi First,". For multiple people, "Hello,".
I like to get to the point and hope to influence others to do the same. I have other coworkers who send me messages in Teams that literally just say "Hello". I mean, come on. You're going to distract me with "Hello" and not ask me a question? I'm not responding to Hello or even can I ask you something. Of course you can ask me something, that's what I'm here for and that's why we have the ability to communicate with each other. Spit it out kid!