How to professionally tell someone to send better emails or use Slack?

Question

There's a remote based colleague who has one of the worst email etiquette I've ever seen. He frequently initiates emails with all the text (usually 100-150 characters) in the subject. In email chains, he frequently fires off 5 emails with one or two words in each of them.

Really, the way he uses it is perfect for Slack, but horrendous for everyone's inbox. I've tried to get him to at least look at Slack by creating a channel for a specific project and asking him explicitly to use it, but he didn't even acknowledge me and continues to use email in this manner. Everyone else involved in the project also tried to give him the hint by using the channel and replying to his emails with "We mentioned that in Slack, have you seen it?" but he still has not acknowledged the existence of it.

I know it's not a huge deal like bad smells or loud noises in the office. However this has gotten annoying enough and gone on for long enough that I want to personally confront him. If I said something very direct like "Sending multiple one word emails in succession clutters everyone's inbox. Instead, let's use Slack for communications of that kind from now on. (Insert link to company's guide for installing Slack app and logging in)." Would that be too harsh or unprofessional?

Answer 1

If I said something very direct like "Sending multiple one word emails in succession clutters everyone's inbox. Instead, let's use Slack for communications of that kind from now on. (Insert link to company's guide for installing Slack app and logging in)." Would that be too harsh or unprofessional?

Not at all.

It reads as polite as possible (in fact, it reads as the "let's continue this discussion in chat" that one can see here on SE) and is asking something reasonable.

Perhaps this person continues to send emails because you continue to reply to them?... Given that you and other colleagues have already told this person in repeated occasions to use Slack, it would be wise to avoid replying to him (and to anyone) that is using emails in a way that goes against the company's policy on email and Slack use.

Answer 2

IMHO, best way to accomplish this task is to get your / his manger involved in the issue

It can be done directly or indirectly,

1. You and few colleagues can mention it to manager on several occasions or as group letter

2. If manager frequently will be exposed to his way of communicating and will be bothered by it, he on his own will request style / medium change