* Mail does not have "quoted_body", "quoted_subject" etc. All of these are accessed via body.encoded, subject.encoded etc
* Every part of a Mail object returns an object, never a string. So Mail.body returns a Mail::Body class object, need to call #encoded or #decoded to get the string you want
* Mail::Message#set_content_type does not exist, it is simply Mail::Message#content_type
* Every mail message gets a unique message_id unless you specify one, had to change all the tests that check for
equality with expected.encoded == actual.encoded to first replace their message_ids with control values
* Mail now has a proper concept of parts, remove the ActionMailer::Part and ActionMailer::PartContainer classes
* Calling #encoded on any object returns it as a string ready to go into the output stream of an email, this
means it includes the \r\n at the end of the lines and the object is pre-wrapped with \r\n\t if it is a
header field. Also, the "encoded" value includes the field name if it is a header field.
* Attachments are only the actual attachment, with filename etc. A part contains an attachment. The part
has the content_type etc. So attachments.last.content_type is invalid. But parts.last.content_type
* There is no idea of a "sub_head" in Mail. A part is just a Message with some extra functionality, so it
just has a "header" like a normal mail message
*2.3.2 [Final] (March 15, 2009)*
* Fixed that ActionMailer should send correctly formatted Return-Path in MAIL FROM for SMTP #1842 [Matt Jones]
