Sandbox HTML parts

[moggers87]

Currently, we do a lot of processing to make HTML parts safe. One of these is to use premailer to inline any CSS found in <style> tags so that email styles don't interfere with the UI.

However, this breaks things like media queries and we have to be careful not to load external styles.

We could use <iframe>s with the srcdoc attribute to allow normal <style> tag operation with media queries and such which would mean fewer styling issues with HTML parts.

[moggers87]

I wonder if this would resolve #404 ?

[moggers87]

Works well, except that we can't set the iframe height to the same height as the content without JS.

[moggers87]

Closing this issue as making Inboxen require users to have JS enabled is not something we want to do.

[moggers87]

Actually, I'm wondering if we could just set the iframes to 80vh (or something similar) with scrollbars enabled which can then be turned off with the same JS that resizes the iframe.

I think this would be fine as most emails only have one MIME part displaying at a time.