IMP 6.1.4.

Can't replicate errors, but the draft message is missing the 
multipart/related attachments, so that's most likely the issue.

Changes have been made in Git (master):

commit 2b025feb0e238915876fa4bd3e352f665a6e8bc0
Author: Michael M Slusarz <slusarz@horde.org>
Date:   Mon Jul 29 17:02:00 2013 -0600

     [mms] Correctly save multipart/related data when saving compose 
message as a draft.

     Bug #12469

  imp/docs/CHANGES    |    2 ++
  imp/lib/Compose.php |    2 +-
  imp/package.xml     |    2 ++
  3 files changed, 5 insertions(+), 1 deletions(-)

http://git.horde.org/horde-git/-/commit/2b025feb0e238915876fa4bd3e352f665a6e8bc0

I attached the whole email file. I thought it'll be enough to 
reproduce the problem.
How did you test this problem?
If you need, I can give you a script which send exactly the same mail 
to your server.

I'm absolutely sure, that this isn't caused by a worm. It happens only 
for this specific mail, regardless which computer I use.

This absolutely cannot be happening if you are resuming a message.   
This can ONLY happen if someone explicitly clicks on an attachment's 
data.  If that is happening automatically on your system when opening 
a draft message, your installation is totally screwed up (and I'd 
actually be a bit worried that there is some sort of worm/click 
hijacking occurring also).

Do not post test accounts - we are not going to login and you just set 
yourself up for spamming.

You need a way of providing a reproducible test case on our system 
independent of how your system is set up (unless you can identify what 
on your system is causing the problem and how it can be worked around).

This is what I get in the webserver log when I open the mail:
---
[Thu Jul 18 11:06:46 2013] [error] [client 192.168.10.200] PHP Fatal 
error:  Call to a member function getPart() on a non-object in 
/usr/local/src/horde/imp/lib/Compose/View.php on line 38
----

And this is what I get when I try to send the mail:
---
[Thu Jul 18 11:07:02 2013] [error] [client 192.168.10.200] PHP Fatal 
error:  Call to a member function getPart() on a non-object in 
/usr/local/src/horde/imp/lib/Compose.php on line 2528, referer: 
https://horde.madalbal.hu/imp/dynamic.php?page=compose&buid=16358&mailbox=SU5CT1g&type=reply_auto&token=jCyRg-yywJjFlxUYd91m-w1&uniq=1374138412143
---

These messages come when the user opens the letter.
I can give you a test account.
How can I insert this message to imp, to test it from another account?

And agree with Jan - I can't reproduce.  Unless you can provide a 
reproducible test case on our system, this ticket will be closed.

This has nothing to do with message composition.  This is someone 
trying to click on an attachment preview.

Yes, I refreshed now, and the problem persists.

Cannot reproduce. Are you sure you are running Git master?

There isn't any horde error.

I found this PHP error 11 times in my webserver log:
---
[Wed Jul 17 13:23:56 2013] [error] [client 192.168.1.4] PHP Fatal 
error:  Call to a member function getPart() on a non-object in 
/usr/local/src/horde/imp/lib/
Compose/View.php on line 38, referer: 
https://horde.madalbal.hu/imp/dynamic.php?page=compose&buid=42&mailbox=RHJhZnRz&type=resume&token=AbfgaRVKWGf6t3LVIMT2tw
1&uniq=1374060231580
---

Please check the Horde, PHP, and web server log files for errors.