The structure and rendering of multipart emails

When marked as multipart/alternative, an email message can contain multiple versions of the same content which allows the email client to render the message in the most appropriate format for the user's device. In most cases, two versions are included: the plaintext version (text/plain) and HTML version (text/html). Other content types such as AMP (text/x-amp-html) are often used in conjunction with the plaintext and HTML versions.

See also

• Email Parser - Parse, inspect, and debug emails online.
• Receiving email with Node.js - How to receive email in Node.js?
• MAIL FROM and RCPT TO vs. the To and From headers - The difference between the email envelope and message headers when it comes to senders and recipients.
• cid URLs for email developers - What are cid URLs and how are they interpreted by email clients?