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### 2.6 Conversion

A (multipart) MIME message can be converted to MML with the `mime-to-mml` function. It works on the message in the current buffer, and substitutes MML markup for MIME boundaries. Non-textual parts do not have their contents in the buffer, but instead have the contents in separate buffers that are referred to from the MML tags.

An MML message can be converted back to MIME by the `mml-to-mime` function.

These functions are in certain senses “lossy”—you will not get back an identical message if you run `mime-to-mml` and then `mml-to-mime`. Not only will trivial things like the order of the headers differ, but the contents of the headers may also be different. For instance, the original message may use base64 encoding on text, while `mml-to-mime` may decide to use quoted-printable encoding, and so on.

In essence, however, these two functions should be the inverse of each other. The resulting contents of the message should remain equivalent, if not identical.