Hey! Hmm - since Mailspring always displays “conversations”, it essentially shows replies along with the message being replied to all the time. They’re not placed in the same IMAP folder, though.
I’m a little hesitant to implement this one because most SMTP gateways place the sent message into the Sent folder on their own (and Mailspring waits for them to do it and then puts it there itself if it’s not done automatically.) I think that if we put sent messages in another folder, you’d probably also see them in the Sent folder sometimes. (At least on Gmail + iCloud, not sure about others offhand.)
I think for now we’ll let Thunderbird have this one but I’ll leave this open in case other folks want to chime in!
(Originally posted by bengotow on GitHub.)