How to Get a Warning Before Emailing Someone Outside Your Company in Gmail

The short answer

If your company uses Google Workspace, Gmail already has an external recipient warning. An admin controls it, it is on by default, and it shows a notice when a thread includes people outside your organization.

What it does not do is stop the send. There is no "Are you sure?" step. The notice sits in the compose window, and you can click Send straight past it. If you want Gmail to actually pause before an email goes outside the company, you need an add-on. Both options are below.

Option 1: Gmail's built-in warning (Workspace only)

What it does

When the setting is on, Gmail warns you when:

• a thread you are replying to includes people outside your organization
• you reply to a message that came from outside
• you start a new email to an outside address

It also adds an "External" label to threads that include outside recipients, so you can see at a glance that a conversation has left the building.

What it skips

Gmail does not warn about an outside address that is already in your company directory or in your own contacts. That second exception matters more than it sounds. Everyone you have emailed before tends to end up in your contacts, so the people you are most likely to send to by mistake (the client with the same first name as a colleague, the old vendor, your personal address) are the ones the warning skips.

It also does not warn for secondary domains or domain aliases your company owns, which is usually what you want.

How to turn it on

This is an admin setting. If you are not a Workspace admin, send these steps to whoever is.

1. Sign in to the Google Admin console.

2. Go to Apps, then Google Workspace, then Gmail, then End User Access.

3. Scroll to the external recipient warnings setting and make sure it is on.

4. To apply it to only part of the company, pick an organizational unit on the left first.

5. Save.

Google says changes can take up to 24 hours, though they usually show up sooner.

Personal Gmail accounts

A personal @gmail.com account has no "organization", so there is no external warning at all. Every address is outside.

Option 2: A real stop before Send

The built-in warning is a sign on the wall. People stop reading signs they see every day. What catches the mistake is a pause at the moment you click Send, with the outside addresses listed so you actually look at them.

Gmail has no setting for that, so it takes an extension. Presend is one. It runs inside Gmail in Chrome and checks every email when you click Send:

1. Install Presend and sign in with your work account. It uses your email domain to tell inside from outside.

2. Open the Presend dashboard and find External recipients in the built-in checks.

3. Set it to Block.

Now, when an email includes anyone outside your domain, Send stops and shows "Hold on" with the outside addresses listed. Click Send anyway if they are right, or Review message to go back and fix the To line. It checks again if you add someone to Cc after you finished writing, which is exactly when most wrong-recipient mistakes happen.

If a stop on every outside email is too much, set the check to Warn or Note instead. The outside addresses still show in the panel next to your draft, without blocking Send.

Two more Gmail settings worth changing

These do not warn you, but they make a wrong-recipient mistake much cheaper:

• Undo Send, up to 30 seconds. Open Settings, then See all settings, then set Undo Send to 30 seconds. Gmail holds the email that long before it really goes.
• Stop autocomplete from learning every address. Under the same General settings, Create contacts for auto-complete decides whether everyone you email gets added to your suggestions. Fewer stale suggestions means fewer wrong picks. More on that in our guide to autocomplete sending email to the wrong person.

And if the email has already gone, here is how to send a correction email without making it worse.