When someone sends a communiqué (and I use that broad term deliberately), let them know you got it.
It may seem like a small thing, but given how many people I know are talking about it, I'd say it's bigger than you might think.
We're all busy. We have a bunch of balls in the air and we like to know that our messages about those balls have been received. I'm not saying you have to respond with a full answer immediately, but I don't think it would kill any of us to quickly shoot back with a "got your message" or "OK" at the very least.
If applicable, I include a time by which the sender can expect a proper reply. And whenever possible, I try to respond via the same channel the sender used. So if you send me an email, I try to respond via email. If you leave a vmail, I try to respond via voice or text to that device.
While this may seem like one of those out-moded common courtesies, the truth is, it's turned out to be a big time-saver. Why? Because it keeps people from calling or emailing or texting me to find out if I got their message. They spend less time tracking me down. I spend less time reading their prodding messages. Everyone wins. A bonus? You're deemed responsive and thoughtful. How's that going to hurt you? Exactly.