Good master Simon,
…coming from here “real” end-to-end by DC coming with an device-server, guided by Master link2tx: Is it the case that is makes it remarkable and worthy to consider bigger?
Having looked a little there are such a smtp-server (maybe Simple SMTP) apps which seems to be pretty small in size. (not able to try app in addition if such works) But generally, if such comes with a “let your device serve” option at setup, and if possible to preconfigurate, it’s possible - told…
-…the opposite, and again the hint that globally people have neither email or wouldn’t know/remember there access pw.