Weird multiline quoted "From" cannot be parsed correctly

[markusramsak]

The "From: " part of this simplified email cannot be parsed correctly.
The result should be: Holger_Akademie für Impulsgebung <[email protected]>

From: =?UTF-8?Q?"Holger=5FAkademie_f=C3=BCr_Impulsge?=
 =?UTF-8?Q?bung"_<[email protected]>?=
To: <[email protected]>
Subject: Nach dem Meisterkreis am 28. April 2016
Date: Thu, 28 Apr 2016 22:05:47 +0200
Message-ID: <[email protected]>

[zbateson]

Hi @markusramsak --

This one too is invalid. It fails on two parts:

1. Semantic parts of a header need to be outside the encoded parts, the encoded parts can encode only within them generally. There is an exception that needs to be made for References/Content-Id headers. See Lack of RFC 1342 support for IdHeader #109 for info on that, but particularly this from RFC 1342:

An encoded-word may replace a "text" token (as defined by RFC 822) in:
(1) a Subject or Comments header field, (2) any extension message
header field, (3) any user-defined message header field, or (4) any
RFC 1341 body part header field (such as Content-Description) for
which the field body contains only "text"s.

That means for example, this is a commented part: (=?UTF-8?=Q?blah?=) but this is not: =?UTF-8?=Q?(blah)?= .

2. For email addresses specifically, they may not be mime-header encoded anyway... my processing may allow it if it's just part of an address (it may not, I can't remember off-hand) but it's not allowed by the RFC: "An 'encoded-word' MUST NOT appear in any portion of an 'addr-spec'." in https://tools.ietf.org/html/rfc2047#section-5

Again, I welcome discussion/examples of other handling, etc...

[markusramsak]

I believe you but these is a part of an real email where this case happenend. I understand if you don't want to handle these cases but then I would try to handle these cases.
These cases are rare but they happen.

[zbateson]

This would also be fixed by prioritizing the mime-encoded part over the quoted part like #159 if it makes sense to do so (should be investigated to see impact/usefulness).