If I sent you a link to this page, please understand that I’m not trying to be a jerk about Slack. I’m trying to minimize the chance that the thing you’re trying to tell, ask, or request of me falls through the cracks.
tl;dr
Here’s a simple, one step flow chart to figure out whether you should Slack or email me.
If you knew that I would not see your message for an hour, would you still send it?
No: Slack me.
Yes: email me.
Please note, the question is not “Would you rather I responded now, or in an hour?” I know the answer to that question. The question is whether the message would still be important in an hour if I hadn’t seen it / answered by then.
Examples
Are you coming to the meeting? We’re in room X.
Would you still send this if you knew I wouldn’t see it for an hour?
No.
Slack away.
Would you take a look at this deck and give me comments?
Would you still send this if you knew I wouldn’t see it for an hour?
Yes.
Please email me.
The site is on fire.
Would you still send this if you knew I wouldn’t see it for an hour?
Probably, but I’d be pretty bummed.
Slack me. Email me for good measure, and maybe give me a call, too.
Rationale / Explanation
It’s true that I don’t love the interrupt-y nature of Slack, but that’s actually not the primary reason behind my request for differentiating what you Slack vs. email me. It’s this:
Email requires effort to forget, Slack requires effort to remember.
If you send me an email, it’s going to sit in my Inbox until I actively move or delete it—even after I’ve read it, it still sits there until I take further action. I’ve spent years working on tools and habits to process my email. I do it several times a day, and try to be very responsive, but when I get busy and can’t process your message immediately, your email sits in my inbox until I catch up and is very hard for me to lose.
Slack, on the other hand, notifies me when a message arrives, but the minute I read the message, it vanishes back into the stew of channels, direct messages, and (my least favorite and the hardest to find) multi-participant direct messages. Yes, I’m aware that I can ask Slack to remind me about a message that I can’t immediately process, and I try to do this as often as possible, but this is “fail deadly” behavior. If I miss that chance, I can’t easily find your message again, and it’s likely to slip through the cracks.
So, for messages that will no longer matter in an hour, it doesn’t matter if I can’t answer them immediately and then lose track of them. They no longer matter! For those, Slack is fine. For anything that will still matter in an hour, email makes it much more likely that I will still be aware of them in an hour if I can’t process them immediately.