Inline Attachments

MIME readers SHOULD mark an attachment MIME part as an inline attachment, as specified in section, when they meet the following criteria:

  • The attachment MIME part MUST be a child of a "multipart/related" MIME entity or the child of a "multipart/mixed" MIME entity that is being used to create an aggregate body, as specified in section

  • The attachment MIME part MUST have a Content-Id or a Content-Location header.

  • The attachment MIME part SHOULD<164> be referenced from an <img> HTML element in the HTML message body.

  • The attachment MIME part SHOULD<165> have one of the following Content-Type header values: "image/jpeg", "image/jpg", "image/pjpeg", "image/gif", "image/bmp", "image/png", or "image/x-png".

Marking attachment MIME parts that do not meet all of these criteria as inline can result in the attachment being hidden from recipients of the message.

A MIME reader MAY<166> set the attInvisibleInHtml flag in the PidTagAttachFlags property ([MS-OXCMSG] section for inline attachments.