The send mail feature is like any other form, it has no memory. And we don’t want a full messaging feature (inbox, outbox, archive, multiple recipients, attachments etc.) here on the devnet, there are so many much better services out there for that.
Adding the sender as “BCC” would cover this use case I think. But it could also annoy everyone else who see no need for it. So unless it’s clear that this makes ultimate sense – I’m reluctant to add this to the roadmap.