Looking for a way to set up an email signature template I can across this page (http://www.howto-outlook.com/howto/signatures.htm#company_logo
) which uses this tag in the image, and seems to make Outlook embed the image in all outgoing emails (which is what we want). If the mce_src tag is not there it doesn't seem to work as expected when you use the file as a signature template.
What I want to know is why. Is this a Microsoft specific code that is undocumented, and what other uses might it have. It seems to get added by a number of Wysiwyg html editors as well.