At one company I got so many messages like that … I just chose not to respond if they didn’t have an actual message.

One of the managers who was not a fan of mine (or anyone) tried to get me in trouble for not responding to his team (they had a habit of handing off tickets they didn’t like the look of to other teams).

I gathered up all the plain “hello” messages and sent it as my response. There were hundreds of them in a single month. My response was that I was working my own tickets and can’t stop to address “hello” messages with no context hundreds of times a month. If they have a critical situation, then they need to say so to get me to break away from my critical situation….