What is the message body of an email? (also known as Content)


The last part of the email message is called the body or the content of the message.

It is what the user will see.


An email has a content part with a mime type (format) that is set with the content-type email header.


Content-Type: text/plain; charset=us-ascii
Content-Type: multipart/alternative; boundary="b1_QOvc4qkAfaq7Tgiq7M6THogyrrifARe0NIlLwqdmT4"

If the content mime type is a multipart type:

  • the email body content is then composed of multiple part that have also a mime type
  • otherwise the content is composed only of one part


Multipart. ie an email may be composed of several part where each part has another associated mime (format)


  • multipart/alternative when sending HTML and TEXT
  • multipart/mixed when sending TEXT and attachments.


The format of advanced designed email is created in special email html document but plain text is always added in the message as a fallback because:

  • not every email client support html
  • or not every user want to see fancy email page

The content of the various parts is interchangeable. The client will show the LAST part if possible.

A body is then composed of a content that has the mime type multipart/alternative where:

  • the HTML part is shown if possible
  • otherwise, the plain-text part is shown

See RFC2046 (Multipurpose Internet Mail Extensions (MIME) Part Two: Media Types) for details of the structure of such a message.

Example: complex multipart alternative with:

  • a text part
  • an html part with 2 subparts:
    • HTML markup
    • and inline image

The parts are delimited with a boundary and the base64 have been truncated but terminate with the classic ==

Content-Type: multipart/alternative; boundary="b1_QOvc4qkAfaq7Tgiq7M6THogyrrifARe0NIlLwqdmT4"

Content-Type: text/plain; charset=utf-8
Content-Transfer-Encoding: base64

Content-Type: multipart/related; boundary="b2_QOvc4qkAfaq7Tgiq7M6THogyrrifARe0NIlLwqdmT4"; type="text/html"

Content-Type: text/html; charset=utf-8
Content-Transfer-Encoding: base64

Content-Type: image/jpeg; name=image1697420268308
Content-Transfer-Encoding: base64
Content-ID: <[email protected]>
Content-Disposition: inline; filename=image1697420268308


Inline image

A part can be an inline image encoded in base64.


Content-Type: image/jpeg; name=image1697420268308
Content-Transfer-Encoding: base64
Content-ID: <[email protected]>
Content-Disposition: inline; filename=image1697420268308

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