I work with my iPad Pro all the time, Agenda primarily but sometimes side by side with the Mail app.
At this time the current behavior when dragging an email into Agenda is it will paste the link to the email. Would it be possible for Agenda to create an .eml email file? (At least the option to do so) I find that for me, it is more useful than a link. I like to transfer every relevant thing to Agenda and just work from there without switching back and forth to other apps. I find it better for me to understand a context of a certain project.
Currently the apps that are able to do this is DevonThink To Go, Keep It Mobile, Anybuffer. There may be others as well.
At this time, my workaround is to export these emails to PDF. (Print email, pinch out, export to Agenda, so many steps… )
Hope this can be considered. Thank you!