MSDN原文，我的翻译能力比较差。 Optional. Describes the content of the body section of the message. It can have one of the following values (the default is "text/plain; charset=us-ascii"): text/plain; charset=us-asciiThis means that this is a regular message, and the body section contains the message text.Example: Content-Type: text/plain; charset=us-asciiapplication/x-ms-tnefThis means that this is a TNEF message and the body section contains the TNEF data of the message.Example: Content-Type: application/x-ms-tnefmultipart/form-data; boundary=boundary-stringThis means that the form and body section have multiple parts, and each part describes a single form field (name, value, and so on). The boundary-string separates multiple parts in the body section (see Body Section).Example: Content-Type: multipart/form-data; boundary=xyz12sssdeeggg
Optional. Describes the content of the body section of the message. It can have one of the following values (the default is "text/plain; charset=us-ascii"):
text/plain; charset=us-asciiThis means that this is a regular message, and the body section contains the message text.Example: Content-Type: text/plain; charset=us-asciiapplication/x-ms-tnefThis means that this is a TNEF message and the body section contains the TNEF data of the message.Example: Content-Type: application/x-ms-tnefmultipart/form-data; boundary=boundary-stringThis means that the form and body section have multiple parts, and each part describes a single form field (name, value, and so on). The boundary-string separates multiple parts in the body section (see Body Section).Example: Content-Type: multipart/form-data;
boundary=xyz12sssdeeggg