Sorry for the confusion - I can confirm it works as advertised :)

Thank you for the quick fix!

Regards,
Jens

https://github.com/horde/horde/commit/e3e7372c92af943819983ee1b6afe6e03fca0785

should this have been included in the code pear-published on 
2013-07-16/-17? I have applied the latest updates, but still see the 
described behavior.

This was already fixed yesterday.

Here are some possibly relevant webmail settings for the user:

new message creation
- text mode emails

replies:
- insert original email into the response
- remove signatures in case of text emails

Concerning "forwards":
- forward original email in the message body

I am logged in using the "dynamic" UI.

When forwarding an e-mail, in the then opening editor window, I see 
the message to add the forwarded e-mail as an attachment (in addition 
to the inline forwarding, which I had set up in my preferences).

When clicking that "click here to attach original message" message, no 
attachments show in the window's attachment list (the list is empty, I 
only have the "add an attachment" option).

When sending the message, the receiver will see the original message 
as attachment, as well as any attachments that were included in the 
forwarded message, so this should be some UI problem. Looking at the 
HTML source of the opened editor window, I can see that the list of 
attachments is actually empty, so this ought not to be some browser 
problem:

      <td id="atctd">
       <span id="upload_limit" style="display:none">Die 
Anhangbegrenzung wurde erreicht.</span>
       <span id="upload_wait" style="display:none"></span>
       <span>
        <label id="compose_upload_add" for="upload">Anhang hinzufügen</label>
        <input id="upload" name="file_upload" type="file" />      </span>
       <ul id="attach_list" style="display:none"></ul>
      </td>

Horde's log shows no obvious error messages, Apache's log reports only "200"s.

This is 100% reproducible.