Version:            (using KDE Devel)
Installed from:    Compiled sources

Today I received an E-mail message, which I wanted to save and add a
note for myself about it (annotation).
I found that I know of no E-mail application, which can do this.

Proposed feature specs:

Terminology:
- External attachment - today's attachment - is received from external
E-mail sources and sent to other users when the message is forwarded.
- Internal attachment - the proposed new kind of attachment - is created
by the user and stays on his computer, and by default is not sent to
anyone outside of his computer.  Another possible name - annotative
attachment.

Operations:
- Add an "internal attachment":
Another operation on E-mail messages (in Inbox and other folders) will
be added.
This operation will be to attach any number of "internal attachments".
- Change the type of an attachment, or a group of selected attachments,
from "internal" to "external" or vice versa.

More details:
1. Those attachments will be associated with the E-mail message as long
as they stay in the folders managed by this E-mail application.
2. They will be marked as "internal" to distinguish them from the
regular ("external") attachments.
3. When reviewing an E-mail message, the user can open an "internal
attachment" the same way he can open an external attachment, and view
its contents (which will typically be a short textual note, but can be
anything, which can be attached to an E-mail message).
4. When an E-mail message is forwarded, it is to be forwarded without
the "internal attachments" (unless they have been re-flagged as external
attachments).

Feature requested by Omer Zak, posted on linux-il:
http://www.mail-archive.com/linux-il%40cs.huji.ac.il/msg45110.html