I was looking for a way to send inline attachments in emails. This way you can for example add your logo to an email.
Unfortunately there seems to be no easy way of doing this. After some googleing I found a ticket for this with a patch that I got working.
For some reason the core developers did not accept the patch. So I decided to make a plugin of it so that I easy could use it in my own applications. The plugin is available at Github if you have the same problem.