"How to find a message's headers"

Every email carries headers: a record of who sent it, every server it passed through, and what the receiving server checked. Your mail app hides them, but every app can show them. Copy all of it, then paste it into Check a message's headers in your workspace, or send it to whoever is helping you.

Headers contain addresses and server names, but not the message's text. If you paste the whole message, we can also check its DKIM signature against the body. Either way, we read it and throw it away.

Gmail

Open the message, choose More (⋮) beside Reply, then Show original. Choose Copy to clipboard.

Outlook on the web and Outlook.com

Open the message, choose More actions (…), then View, then View message details. Select everything in the box and copy it.

Outlook for Windows

Open the message in its own window, choose File, then Properties. The headers are in the Internet headers box at the bottom. Click in it, select all and copy.

Outlook for Mac

Select the message, then choose Message, then View source. Copy everything shown.

Apple Mail on a Mac

Select the message, then choose View, then Message, then All Headers. For the whole message, choose Raw Source instead.

iPhone and iPad

The Mail app can't show headers. Forward the message to an address you read on a computer, or open it in your provider's webmail, then follow the steps above. Forwarding changes the headers, so the webmail route is better when you can.

In healthcheck.email

From your workspace's home, choose Check a message's headers and paste what you copied. You'll get a plain answer first: whether it passed SPF, DKIM and DMARC, where it waited, and how Microsoft scored it. Every hop and header is one step below.