How to Get an External Recipient Warning in Outlook (Pop-Up Before Send)

Which Outlook do you have?

The answer depends on which Outlook you write in, because they do not share features:

• Classic Outlook for Windows, the desktop app most companies have used for years
• New Outlook for Windows, which is really Outlook on the web in an app window
• Outlook on the web, at outlook.office.com in a browser

Here are the three ways to get a warning, from free and built in to a proper stop before Send.

Option 1: The External Recipients MailTip (built in, free)

Microsoft 365 has a feature called MailTips: small notices that appear above the To line while you write. One of them tells you that some recipients are outside your organization, and names them.

It works in classic Outlook, new Outlook and Outlook on the web, and it costs nothing. But two limits matter:

• It is a notice, not a pop-up. You can click Send without ever looking at it.
• Only an Exchange admin can turn it on, and only for the whole organization.

How an admin turns it on

In Exchange Online PowerShell:

The first command after connecting shows the current values. Sources disagree on whether the external tip is on by default, so check before you change anything. MailTipsAllTipsEnabled must also be true, or no MailTips show at all.

Option 2: A macro for classic Outlook (free, one person)

If you only want the pop-up for yourself and you use classic Outlook on Windows, a short VBA macro can do it. It runs every time you click Send, and if any recipient is outside your domain, it asks you to confirm.

1. In Outlook, press Alt + F11 to open the VBA editor.

2. In the left pane, open Project1, then Microsoft Outlook Objects, then double-click ThisOutlookSession.

3. Paste this, and change yourcompany.com to your own domain:

4. Save, close the editor and restart Outlook.

The catches:

• Macros must be allowed. Many companies block unsigned macros. You can sign it yourself with the SelfCert tool that comes with Office, but if IT blocks macros by policy, it will not run.
• Classic Outlook only. New Outlook and Outlook on the web do not run VBA at all.
• It only knows one domain. If your company uses two, add a second check.

Option 3: An add-in that stops the send

For a whole company, or for new Outlook and the web, you want an add-in.

VIPRE SafeSend is the best-known one. It shows a confirmation when an email is addressed outside your domain, lists the recipients and attachments, and makes you confirm before it goes. IT deploys it to everyone and licenses it per user per year. It is a good fit when the whole company lives in Outlook. We compare it in detail in our SafeSend alternative page.

[Presend](/) does the same stop in Outlook on the web and in Gmail, as a Chrome extension. Set the built-in External recipients check to Block on the Presend dashboard, and Send stops with "Hold on" and the outside addresses listed, with Send anyway and Review message. It also runs the other checks people want at that moment: a missing attachment, a password or card number pasted by mistake, a banned phrase. It does not run inside the classic Outlook desktop app.

Which one to pick

Whichever you choose, also turn on Undo send in Outlook on the web and new Outlook: Settings, then Mail, then Compose and reply. It gives you up to 10 seconds to take an email back.