I haven't, no.
How would one go about referencing the images placed there in the HTML footer though? What I am trying to avoid is having something like <img src="http://myserver/whatever/theimage.png"> because most mail clients will not display the images by default and instead insist on you clicking a "display external images" button.
What I am trying to do is have images that are referenced like this:
<img src="cid:12345">
Then additional mime parts that contain the image like this:
------=_Part_374_21510038.1268676246147
Content-Type: image/jpeg; name="image.jpg"
Content-Transfer-Encoding: base64
Content-Disposition: attachment; filename="image.jpg"
Content-ID: <12345>
<base 64 image data>
The trouble I am having is what ever I put in the global HTML disclaimer just gets put into the text/html part of the email and I cant figure out how to get an attachment added on the fly with a known content ID so I can reference it in my HTML.
Zimbra recently added this feature for per user signatures. Its discussed in this bug -
Bug 25797 – RFE: inline/embeded logos in the signature and the fix was the implementation of the "insert image" button on the signature configuration screen that takes an image on the fly from your briefcase and adds it as an attachment.
Hope that makes sense?