this is probably a common question but still looking for an answer.

How can i insert an image to all email outgoing from the server, it can not be done via the signature setting. I have already tried the
Code:
<img src ="http://domain.uk/images/ident.jpg">
but that just displays the image link, not the actual image
prefered via horde or roundcube. this is to prove the image came from the users server