I have been using DeltaChat for a while and it is very useful for me.
I also frequently use email daily. Both email client and DC installed on laptop and phone.
When I got email in DC, I have to switch to email client to reply or forward.
So, Technically speaking, is that possible when someone send me a email (with subject), It behaves like an email, just like other email apps. I could reply or forward in DC.