Short answer
Install the extension, open Gmail, click the ID button beside the message,
and paste the copied locator wherever you need the source reference. When
Gmail exposes the RFC header, the locator uses rfc822msgid:.
Steps
- Install Gmail Message ID & Thread ID Copier from the Chrome Web Store.
- Open Gmail in Chrome.
- Find the email you want to reference.
- Click the small ID button added by the extension.
- Paste the copied locator into an AI prompt, support ticket, CRM note, or source ledger.
Why use a Message-ID?
A Gmail subject line or sender search can become ambiguous. A copied Message-ID or Gmail message locator gives a tool or teammate a stable handle back to the exact email.