@art8
Sorry can't reproduce. We can try to think of some way to diagnose this further, but so far, nothing.
BTW, I had to fix a bunch of headers compared to what you posted -- remove the blank line in the middle of one header (the one I asked about above), and fix the indentation on others. Before I did, these messages wouldn't open right in Thunderbird or Fastmail web mail.
I'm not sure if your messages were like that to begin with (meaning malformed) or they got changed when you copied / pasted.
What I ended up with it below:
Message 1, the original was *last* in your post:
In-Reply-To: <op.yu61x5jinwub7b@john-pc>
References: <58964aca.0faa370a.645b7.50c3SMTPIN_ADDED_MISSING@mx.google.com>
<CAM4SxfgGgTFBnfy6dQ6MjJFB=Cg5o62owAz+7TaVydeUwRXL0w@mail.gmail.com>
<op.yu61x5jinwub7b@john-pc>
From: A Y <h@gmail.com>
Date: Mon, 6 Feb 2017 00:15:46 +0800
Message-ID: <CAM4Sxfj+NZjkO9sB=2a6dZN4Kgs3FF9-Q+7f+XyMYGkw3N9kXg@mail.gmail.com>
Subject: Re: RMZ
To: J R <p@san.rr.com>
Cc: D L <rr@aol.com>, A Jet <a@gmail.com>, JIM
HOULIHAN <j@hotmail.com>
Content-Type: text/plain
Message 1
Message 2:
From: J H <j@hotmail.com>
To: A Y <h@gmail.com>, J R
<p@san.rr.com>
CC: D L <rr@aol.com>, A Jet <a@gmail.com>
Subject: Re: RMZ
Thread-Topic: RMZ
Thread-Index: AQHSf4L8p0xwnOKgE0qb8Xbx1AMmM6FajhGAgAAJHwCAAAOf8A==
Date: Sun, 5 Feb 2017 16:29:21 +0000
Message-ID: <MWHPR06MB26721DA0CF059D605244CDAEAC410@MWHPR06MB2672.namprd06.prod.outlook.com>
References: <58964aca.0faa370a.645b7.50c3SMTPIN_ADDED_MISSING@mx.google.com>
<CAM4SxfgGgTFBnfy6dQ6MjJFB=Cg5o62owAz+7TaVydeUwRXL0w@mail.gmail.com>
<op.yu61x5jinwub7b@john-pc>,<CAM4Sxfj+NZjkO9sB=2a6dZN4Kgs3FF9-Q+7f+XyMYGkw3N9kXg@mail.gmail.com>
In-Reply-To: <CAM4Sxfj+NZjkO9sB=2a6dZN4Kgs3FF9-Q+7f+XyMYGkw3N9kXg@mail.gmail.com>
Accept-Language: en-US
Content-Language: en-US
Content-Type: text/plain
MIME-Version: 1.0
Message 2
Message 3:
Content-Type: text/plain
To: "A Y" <h@gmail.com>
Cc: "D L" <rr@aol.com>, "A Jet" <a@gmail.com>,
"J H" <j@hotmail.com>
Subject: Re: RMZ
References: <58964aca.0faa370a.645b7.50c3SMTPIN_ADDED_MISSING@mx.google.com>
<CAM4SxfgGgTFBnfy6dQ6MjJFB=Cg5o62owAz+7TaVydeUwRXL0w@mail.gmail.com>
<op.yu61x5jinwub7b@john-pc>
<CAM4Sxfj+NZjkO9sB=2a6dZN4Kgs3FF9-Q+7f+XyMYGkw3N9kXg@mail.gmail.com>
Date: Sun, 05 Feb 2017 10:21:04 -0800
MIME-Version: 1.0
From: aztec <p@san.rr.com>
Organization: aztec
Message-ID: <op.yu689etmnwub7b@john-pc>
In-Reply-To: <CAM4Sxfj+NZjkO9sB=2a6dZN4Kgs3FF9-Q+7f+XyMYGkw3N9kXg@mail.gmail.com>
User-Agent: Opera Mail/1.0 (Win32)
Message 3