Google executive chairman Eric Schmidt and former SVP Jonathan Rosenberg shared nine email "rules" in the book How Google Works. The top item: Respond quickly.
It really does work. I'm always impressed by people who respond immediately to emails, consistently. They give you the sense that they're on top of their game, not that they're hovering over their email client all the time. As the Google execs explain in Time:
There are people who can be relied upon to respond promptly to emails, and those who can’t. Strive to be one of the former. Most of the best—and busiest—people we know act quickly on their emails, not just to us or to a select few senders, but to everyone. Being responsive sets up a positive communications feedback loop whereby your team and colleagues will be more likely to include you in important discussions and decisions, and being responsive to everyone reinforces the flat, meritocratic culture you are trying to establish. These responses can be quite short—“got it” is a favorite of ours. And when you are confident in your ability to respond quickly, you can tell people exactly what a non-response means. In our case it’s usually “got it and proceed.” Which is better than what a non-response means from most people: “I’m overwhelmed and don’t know when or if I’ll get to your note, so if you needed my feedback you’ll just have to wait in limbo a while longer. Plus I don’t like you.”
I've been guilty of responding to emails long past decent consideration, but now my new mantra is "Strive to respond quickly." Google's advice to strive to respond to email quickly isn't just about managing your inbox. It's about demonstrating your responsibility and having consideration for the sender.
That doesn't mean I'm hovering over my inbox all the time--I'm setting up filters so only the most important contacts and messages send a notification--but that when my normal procrastination response of "I'll reply later" comes up, I try to remember this advice. Even if it's just a quick "Thanks, got it," that response may mean more to the recipient than we think.