The RoundCube UI has support for some basic headers. You can "Add CC", "Add Bcc", "Add Reply-To" and "Add Followup-To". You can look for these strings in the code and extend the UI with headers of your choice. A possibility would be "Add Arbitrary Header", where q quick and dirty way to implement it would be to let the user enter the header using "Name: value" syntax, and parse it out. You could repeat that button three times so the user can add up to three custom headers.
As far as PGP headers go, you really don't want users to be mucking around with headers; PGP support ought to be integrated into the client.
huh no, you have got that wrong, there is an official header type PGP which is where people can put in URL's to go to get persons keys etc,
Adding a custom header if the users want to, is what I was inquiring about, seems there is no such beast, so we may need to look at alternatives, squirelmail did this years ago, so I was surrpised roundcube doesnt. thanks anyway
You could probably do this in a plugin. There is two ways to approach this as far as I can see.
The first is the easiest. If you want users to be able to set a static outgoing header on every sent message, you could write a plugin that hooks into the settings, and into message_outgoing_headers. This is pretty trivial at first glance.
If you want users to be able to set any header on compose, it gets a bit more tricky. You'd probably need to hook into a render hook, and add your html, or maybe add some html through javascript. Then again hook into message_outgoing_headers, read your post data, and add this to the headers array.
The great thing about roundcube is that you can do almost anything in plugins.
Cor