Outlook 2013 and Outlook 2016

1. Launch Outlook.
2. Open the email by double-clicking it to view it in a separate window.
3. Click on File.
4. From the sidebar, choose Info.
5. Click the Properties button.
6. Look for the Internet headers section to view all header data.

Outlook 2011 (Mac)

1. Start Outlook.
2. Right-click (or hold Control and click) on the email in your inbox.
3. Choose View Source.
4. This will open a new window showing the full message source, including header details.

Outlook Web App (Office 365)

1. Open the email you’d like to inspect.
2. Click the dropdown arrow next to Reply All in the upper-right corner.
3. Select View Message Details from the menu.
4. A popup labeled “Message Details” will display the email headers.

Apple Mail

1. Launch Apple Mail.
2. Click on the email you want to examine.
3. From the top menu, choose View, then Message.
4. Select All Headers (or Long Headers in earlier versions).
5. The full message source, including headers, will appear in a new window.

Gmail

1. Open the email from your inbox.
2. Click the three-dot menu (ellipsis) in the top-right corner of the message.
3. Choose Show original.
4. A new browser tab will open, showing the complete email header information.