Slack Connect DMs: how to message someone at another company

A Slack Connect DM is a direct message with someone at another company, inside Slack instead of email. It is part of Slack Connect, the same feature that lets companies share channels. This guide covers how to start one, the settings that can block it, and when a shared channel is the better choice.

What a Slack Connect DM is

It works like any other direct message, except the other person works somewhere else and joins from their own workspace. Neither of you gets access to the other company's channels. Before you can talk, one of you sends an invitation and the other has to accept it.

Unlike shared channels, DMs are not limited to paid plans. Slack's help center says that on any Slack plan, you can start a DM by sending an invitation or accepting one. Once connected, your external conversations sit in the External Connections section of your sidebar by default, so they do not get lost among internal ones.

Start a DM with someone outside your company

On desktop:

1. From Home, click Directories.
2. Click External at the top of the page.
3. Click Start a DM in the top right.
4. Enter the email address of the person you want to message.
5. Click Send Invitation.

On mobile, tap the compose button on the Home tab, choose Message with external people, and share the invitation. If you do not see Directories on desktop, look for External connections in the sidebar instead.

There is a shortcut worth knowing. If you already share a channel with someone at the other company, you can DM them without sending an invitation. Just open a message to them like you would with a colleague.

Accept, decline or block an invitation

When someone invites you, you can accept, decline, or ignore it. If the invitation comes from someone you do not want to hear from, Slack lets you stop getting future invitations from that person. That matters, because a Slack invitation can arrive from anyone who has your work email address.

When the option is missing

If you cannot send or accept an invitation, the cause is almost always a setting. Slack's advice is to find an owner or admin and ask for help.

Admins have several controls here. Workspace owners, and org owners and admins on Enterprise plans, can turn Slack Connect DMs on or off. They can also choose who may send and accept invitations, and restrict invitations from unverified organizations. Those settings do not affect DMs with people you already share a channel with. That is why a colleague may be able to message a partner when you cannot start a fresh DM.

Group DMs with people from other companies

You can include several people from more than one company in a group DM, with one condition: everyone must be in at least one channel together. In practice, that means a shared channel comes first. If you find yourself wanting a group DM with a partner, a small shared channel is usually the cleaner choice anyway.

DM or shared channel?

A DM is the quickest way to reach one person. For anything that involves a customer relationship, it is often the wrong place.

The problem with DMs for customer work is that they belong to one person. Say a customer asks your account manager a question in a DM, and the account manager is on holiday. Nobody else knows the question exists. A customer conversation in one person's DMs has no backup.

If a customer keeps using DMs, move them gently. Reply to the DM, then suggest the channel:

Happy to help with this. I've posted it in #ext-northwind so Sam can pick it up if I'm away, and we'll answer there.

Our guide on how to create an external Slack channel covers setting one up if you do not have one yet.

End a Slack Connect DM

To end a DM, open it, click the person's name in the conversation header, then click Remove connection and confirm. On mobile, tap their name at the top of the screen and do the same. The conversation is archived, but you can still read the messages and files.

Admins have a broader option. Owners and admins on Business+ and Enterprise plans can end DMs by disconnecting the external user entirely, which is useful when someone leaves a partner company.

If an invitation fails on the other side, our guide to Slack Connect invitations that cannot be accepted works through the usual causes. For bringing outsiders in more permanently, compare Slack Connect and guest accounts, and for running shared channels well, see the main Slack Connect guide.

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