Fixed in Git and will be in the next Horde_Mime release shortly.

Changes have been made in Git (master):

commit 51f860cf23fbe0f469a0ceb06a0093672fba20a8
Author: Michael J Rubinsky <mrubinsk@horde.org>
Date:   Thu Dec 4 18:51:20 2014 -0500

     Add test for Bug: 13709

  framework/Mime/test/Horde/Mime/MailTest.php |   34 
+++++++++++++++++++++++++++
  1 files changed, 34 insertions(+), 0 deletions(-)

http://github.com/horde/horde/commit/51f860cf23fbe0f469a0ceb06a0093672fba20a8

Changes have been made in Git (master):

commit 364376232e02b586e5f1132d24de63cc67195d84
Author: Michael J Rubinsky <mrubinsk@horde.org>
Date:   Thu Dec 4 16:34:05 2014 -0500

     Bug: 13709 Check for lines > 998 characters before ENCODE_8BIT.

  framework/Mime/lib/Horde/Mime/Part.php |   10 +++++-----
  1 files changed, 5 insertions(+), 5 deletions(-)

http://github.com/horde/horde/commit/364376232e02b586e5f1132d24de63cc67195d84

I've just seen this behaivour too.. For me it happened when I replied 
to an email on my Android Nine client and I inserted a yellow graphic 
of a smiley face from the Samsung keyboard. With the smiley the email 
wouldn't send with the error above, but as soon as I edited the 
message and resent it without the smiley, it sent straight away.

Just thought I'd add this comment in case it helps shed any more light..

Tim

The content of the email that is stripped is probably the culprit. As 
Michael S. has said, it probably contains NULL characters. I'd need to 
see the entire email to investigate.  Feel free to email my directly.

Normally I would say if it's broken input (a badly formed email), of 
course it's going to be broken output, but as with most things 
ActiveSync, once something goes wrong it can take down the entire 
client, so....

I'll look at this when I can, but the next week or so I have a pretty 
tight schedule.

Hi again,

i stumbled over the same behavior again and can now provide some more details.

Composing a new mail on my Android device and sending this one is working.
Answering a mail on my Android device is not working, but it seems to 
be related to the mail i try to answer.
If I answer a mail I've sent from my device before it works, but I 
have at least one other mail I can't answer with the error:
<horde.log>
EMERG: HORDE Server does not support binary message data. [pid .... on 
line 596 of "/..../horde/libs/Horde/Smtp.php"]

<device.log>
2014-11-24T13:40:43+01:00 INFO: [9686] SMARTREPLY request received for 
user .....
2014-11-24T13:40:43+01:00 INFO: [9686] Device entry exists for ....., 
updating userAgent and version.
2014-11-24T13:40:43+01:00 INFO: [9686] Request being handled for 
device: ....., Supporting protocol version: 14.1, Using 
Horde_ActiveSync v2.x.y-git
2014-11-24T13:40:43+01:00 INFO: [9686] GET VARIABLES: Array
(
     [Cmd] => SmartReply
     [User] => .....
     [DeviceId] => .....
     [DeviceType] => Android
)

2014-11-24T13:40:43+01:00 INFO: [9686] Handling SENDMAIL command with Wbxml.
2014-11-24T13:40:43+01:00 DEBUG: [9686] I  <ComposeMail:SmartReply>
2014-11-24T13:40:43+01:00 DEBUG: [9686] I   <ComposeMail:ClientId>
2014-11-24T13:40:43+01:00 DEBUG: [9686] I     SendMail-116931579868476
2014-11-24T13:40:43+01:00 DEBUG: [9686] I   </ComposeMail:ClientId>
2014-11-24T13:40:43+01:00 DEBUG: [9686] I   <ComposeMail:SaveInSentItems />
2014-11-24T13:40:43+01:00 DEBUG: [9686] I   <ComposeMail:Source>
2014-11-24T13:40:43+01:00 DEBUG: [9686] I    <ComposeMail:ItemId>
2014-11-24T13:40:43+01:00 DEBUG: [9686] I      426997
2014-11-24T13:40:43+01:00 DEBUG: [9686] I    </ComposeMail:ItemId>
2014-11-24T13:40:43+01:00 DEBUG: [9686] I    <ComposeMail:FolderId>
2014-11-24T13:40:43+01:00 DEBUG: [9686] I      F6d875398
2014-11-24T13:40:43+01:00 DEBUG: [9686] I    </ComposeMail:FolderId>
2014-11-24T13:40:43+01:00 DEBUG: [9686] I   </ComposeMail:Source>
2014-11-24T13:40:43+01:00 DEBUG: [9686] I   <ComposeMail:MIME>
2014-11-24T13:40:43+01:00 DEBUG: [9686] I     [1085 bytes of content]
2014-11-24T13:40:43+01:00 DEBUG: [9686] I   </ComposeMail:MIME>
2014-11-24T13:40:43+01:00 DEBUG: [9686] I  </ComposeMail:SmartReply>
2014-11-24T13:40:43+01:00 ERR: Server does not support binary message data.

Here are some details of the problematic mail i try to answer (some 
parts stripped for privacy):
##### start
From: someone <...@...>
To: Joerg Pulz <Joerg.Pulz@frm2.tum.de>
Date: Mon, 24 Nov 2014 13:20:14 +0100
Subject: .....
Thread-Topic:.....
Thread-Index: AdAH4P4h3JsrvGu7QKGY2ASKzfv5sg==
Message-ID: <375CC0FA-6150-47D6-A6ED-96F98C651DDF@kit.edu>
Accept-Language: de-DE, en-US
Content-Language: en-US
X-MS-Has-Attach:
X-MS-TNEF-Correlator:
acceptlanguage: de-DE, en-US
Content-Type: multipart/alternative;
        boundary="_000_375CC0FA615047D6A6ED96F98C651DDFkitedu_"
MIME-Version: 1.0
X-Greylist: .....

--_000_375CC0FA615047D6A6ED96F98C651DDFkitedu_
Content-Type: text/plain; charset="Windows-1252"
Content-Transfer-Encoding: quoted-printable

Plain message text.

--_000_375CC0FA615047D6A6ED96F98C651DDFkitedu_
Content-Type: text/html; charset="Windows-1252"
Content-Transfer-Encoding: quoted-printable

HTML message text.

--_000_375CC0FA615047D6A6ED96F98C651DDFkitedu_--
##### end

I can provide the full mail directly on request.

Please reopen this ticket and increase priority, because when a mail 
is in the "Outbox" that produces the above mentioned error I'm unable 
to send any other mail using my Android device until I delete the 
problematic one from "Outbox".

Thanks for your help
Joerg

Thanks for your comments.

After removing the device from the ActiveSync devices and 
resynchronizing everything is working again.
Don't know what happened to get these results but after all i'm able 
to send emails using my mobile.
Just curious, now i see the answered flags on my mobile correctly 
again, this was also not working before the complete resync.

Anyway, thanks for your help and time.
Please mark this as solved/closed.

The only way this error could be triggered is if the message contains 
nulls or is > 998 characters in a single line, if that helps.

Cannot reproduce.

Does this happen with every email sent via the client, or just certain 
emails? If the latter, please provide an email that exhibits this 
behavior.

Today i discovered a strange problem when trying to send an email 
using an Android device.

The email stays in the devices Outbox and the horde.log shows the 
following error:

EMERG: HORDE Server does not support binary message data. [pid ..... 
on line 596 of "/.../horde/libs/Horde/Smtp.php"]

We are currently running the latest GIT version  (pulled from github 
just some minutes ago).
I can't say the exact date/revision when this error occurred first, 
but it was working fine in previous revisions.
I guess it has something to do with the latest changes to the Smtp framework.

Sending email using the WebUI is working fine.

SMTP server is sendmail and reports the following:

250-ENHANCEDSTATUSCODES
250-PIPELINING
250-8BITMIME
250-SIZE 31457280
250-DSN
250-ETRN
250-AUTH PLAIN LOGIN GSSAPI
250-STARTTLS
250-DELIVERBY
250 HELP

Any help or fix is much appreciated.