When a messaging transport downloads and saves HTML-formatted content, it uses one of two approaches:
- The transport stores MIME, and includes the HTML in the message MIME stream. Such HTML messages have a MIME part with "
Content-Type: text/html;" in the header. This approach applies to POP and IMAP, and is the approach taken by Microsoft for the built-in e-mail messaging transport.
- The transport stores body streams directly into messages, storing the non-Unicode HTML byte-stream into the PR_BODY_HTML_A message content property. This is the approach commonly used in custom transports.
When a transport opens a message from a message store, and makes the message available for a user to add content to it and then resend it, the HTML stream containing the user's new content is stored in the PR_BODY_HTML_A property.
When e-mail is composed on the mobile device, the PR_BODY_HTML and PR_BODY_HTML_W properties are typically left empty, and the byte-stream version of the HTML body is saved in PR_BODY_HTML_A.