How many type of Content-Type and Content-Encoding-Trafering in email and how to decode it?

I am using ImapX lib to recieve email开发者_运维百科 from Gmail.

I get many type of Content-Type and Content-Encoding-Trafering of Body of email. How to decode it?

The MIME standards are documented in RFCs 2045 through 2048. You probably don't want to read all of them, but you certainly should have a basic understanding of MIME before you attempt to process it. http://en.wikipedia.org/wiki/MIME is a good starting point.

The Content-Transfer-Encoding can have one of five distinct values; out of those, 7bit, 8bit, and binary do not need any decoding (they differ in what you can assume about character sets and line lengths; the difference between 8bit and binary is that 8bit is guaranteed to have lines of limited length; although you certainly see this violated in the wild sometimes).

For quoted-printable and base64 you need decoding; but any reasonably modern programming language already has library functions for this.

The Content-Type hierarchy is basically unlimited. There is a limited number of top-level types (text, image, audio, application, etc) and a standard set of subtypes (text/plain, text/html, etc) but more are being registered, and the standard doesn't require a type to be registered. Anyway, these do not typically need decoding; they declare the type of the content, so that the recipient knows what to do with them. The generic catch-all is application/octet-stream which basically means "here is a blob of data; hopefully the human recipient knows what to do with this" and for many types, there is no sensible default action other than to download to the local disk. All general-purpose email clients will display text/plain directly to the user, unless the Content-Disposition requires otherwise, and most modern clients will display text/html and several other types inline. But what you want to do with the content is first and foremost dictated by what kind of application you are coding.