Mail with receipts.
An email client with the receipts Apple left out. Free and open source.
Be first in line
One email when it’s ready. No spam, ever.
Seen.
Request a read receipt. Know if it was opened, not just sent.
Delivered.
Request a delivery receipt. Know it hit the mailbox, not the void.
Later.
Snooze it. Send it Monday. Undo a send that wasn’t ready.
Yours.
Free, open source. No subscription. No “upgrade to see if they read it.”