zimbra web client: open compose of a draft via url

[freepath]

Hi all,
i would like to open, via url, the compose view of zimbra web ui for an existing draft message. The use case is something like:
1. inside an external application, via web services, we create a draft message
2. the web browser is opened with such draft message in edit view.

I can open a message specifiing its id (adding id=<dbid> on url) in 'read-only' view, or i can open a generic compose view with a new message, but i did not find a way of editing a pre-existing draft.
Is it possible to do it ?

Regards