Content-ID and Message-ID Uniform Resource Locators
CIDMID-URL
HTML
Hypertext Markup Language
URL
Uniform Resource Locator
MIME
Multipurpose Internet Mail Extensions
The Uniform Resource Locator (URL) schemes, "cid:" and "mid:" allow references to messages and the body parts of messages. For example, within a single multipart message, one HTML body part might include embedded references to other parts of the same message. [STANDARDS-TRACK]