Thanks Sébastien Ramage for the report.

Thanks Tim Graham for the review.

Thanks Tim Graham for the review.

These functions do nothing on Python 3.

Thanks Tim Graham for the review.

Thanks Tim Graham and Simon Charette for the reviews.

Thanks Tim Graham for the review.

Thanks Pavel Pokrovskiy for the report and Tim Graham for the review.

Thanks Jarek Glowacki for the report.

Fixed #27368 -- Modifed BaseEmailBackend.__enter__() to close the connection if an exception occurs.

Fixes unclosed socket ResourceWarning in mail test.

Thanks Claude Paroz for the review.

Thanks Tim Graham for the review.

The Content-Transfer-Encoding header won't be repeated, so checking
the header is sufficient.

The test wouldn't pass if a mail server is running on the system.

Passing an Unicode string on Python 2 was crashing the connection.
Thanks slavugan@gmail.com for the report, and Tim Graham for the review.

The fallback logic which allows non-UTF-8 encoded files to be passed to
attach_file() even when a `text/*` mime type has been specified is
moved to attach(). Both functions now fall back to a content type of
`application/octet-stream`.

A side effect is that a file's content is decoded in memory instead of
opening it in text mode and reading it into a string.

Some mimetype-related logic in _create_attachment() has become
obsolete as the code moved from attach_file() to attach() already
handles this.

The test now also checks whether the sent message's attachment has the expected
name, content and mime type.

Thanks Tim Graham for the review.

When EMAIL_USE_LOCALTIME=True, send emails with a Date header
in the local time zone.

On Python 3, sending emails failed for addresses containing non-ASCII
characters due to the usage of the legacy Python email.utils.formataddr()
function. This is fixed by using the proper Address object on Python 3.

Thanks NotSqrt for the excellent report and Tim Graham for the review.

Thanks tkrapp for the report and Tim Graham for the review.