##
7.1.11 Package History

This table describes the release history of the email package, corresponding to the version of Python that the package was released with. For purposes of this document, when you see a note about change or added versions, these refer to the Python version the change was made it, not the email package version. This table also describes the Python compatibility of each version of the package.

email version | distributed with | compatible with
--- | --- | ---
`1.x` | Python 2.2.0 to Python 2.2.1 | no longer supported
`2.5` | Python 2.2.2+ and Python 2.3 | Python 2.1 to 2.5
`3.0` | Python 2.4 | Python 2.3 to 2.5
`4.0` | Python 2.5 | Python 2.3 to 2.5

Here are the major differences between `email` version 4 and version 3:

- All modules have been renamed according to PEP 8 standards. For example, the version 3 module `email.Message` was renamed to `email.message` in version 4.

- A new subpackage `email.mime` was added and all the version 3 `email.MIME*` modules were renamed and situated into the `email.mime` subpackage. For example, the version 3 module `email.MIMEText` was renamed to `email.mime.text`.

  Note that the version 3 names will continue to work until Python 2.6.

- The `email.mime.application` module was added, which contains the `MIMEApplication` class.

- Methods that were deprecated in version 3 have been removed. These include `Generator.__call__()`, `Message.get_type()`, `Message.get_main_type()`, `Message.get_subtype()`.

- Fixes have been added for RFC 2231 support which can change some of the return types for `Message.get_param()` and friends. Under some circumstances, values which used to return a 3-tuple now return simple strings (specifically, if all extended parameter segments were unencoded, there is no language and charset designation expected, so the return type is now a simple string). Also, %-decoding used to be done for both encoded and unencoded segments; this decoding is now done only for encoded segments.

Here are the major differences between `email` version 3 and version 2:

- The `FeedParser` class was introduced, and the `Parser` class was implemented in terms of the `FeedParser`. All parsing therefore is non-strict, and parsing will make a best effort never to raise an exception. Problems found while parsing messages are stored in the message's defect attribute.

- All aspects of the API which raised `DeprecationWarning`s in version 2 have been removed. These include the _encoder argument to the `MIMEText` constructor, the `Message.add_payload()` method, the `Utils.dump_address_pair()` function, and the functions `Utils.decode()` and `Utils.encode()`.

- New `DeprecationWarning`s have been added to: `Generator.__call__()`, `Message.get_type()`, `Message.get_main_type()`, `Message.get_subtype()`, and the strict argument to the `Parser` class. These are expected to be removed in future versions.

- Support for Pythons earlier than 2.3 has been removed.

Here are the differences between `email` version 2 and version 1:

- The `email.Header` and `email.Charset` modules have been added.

- The pickle format for `Message` instances has changed. Since this was never (and still isn't) formally defined, this isn't considered a backward incompatibility. However if your application pickles and unpickles `Message` instances, be aware that in `email` version 2, `Message` instances now have private variables _charset and _default_type.

- Several methods in the `Message` class have been deprecated, or their signatures changed. Also, many new methods have been added. See the documentation for the `Message` class for details. The changes should be completely backward compatible.

- The object structure has changed in the face of message/rfc822 content types. In `email` version 1, such a type would be represented by a scalar payload, i.e. the container message's `is_multipart()` returned false, `get_payload()` was not a list object, but a single `Message` instance.

  This structure was inconsistent with the rest of the package, so the object representation for message/rfc822 content types was changed. In `email` version 2, the container does return `True` from `is_multipart()`, and `get_payload()` returns a list containing a single `Message` item.

  Note that this is one place that backward compatibility could not be completely maintained. However, if you're already testing the return type of `get_payload()`, you should be fine. You just need to make sure your code doesn't do a `set_payload()` with a `Message` instance on a container with a content type of message/rfc822.

- The `Parser` constructor's strict argument was added, and its `parse()` and `parsestr()` methods grew a headersonly argument. The strict flag was also added to functions `email.message_from_file()` and `email.message_from_string()`.

- `Generator.__call__()` is deprecated; use `Generator.flatten()` instead. The `Generator` class has also grown the `clone()` method.

- The `DecodedGenerator` class in the `email.Generator` module was added.

- The intermediate base classes `MIMENonMultipart` and `MIMEMultipart` have been added, and interposed in the class hierarchy for most of the other MIME-related derived classes.

- The _encoder argument to the `MIMEText` constructor has been deprecated. Encoding now happens implicitly based on the _charset argument.

- The following functions in the `email.Utils` module have been deprecated: `dump_address_pairs()`, `decode()`, and `encode()`. The following functions have been added to the module: `make_msgid()`, `decode_rfc2231()`, `encode_rfc2231()`, and `decode_params()`.

- The non-public function `email.Iterators._structure()` was added.