@penguin42 @andrew @neil My key issue here is that there should be a specific point that sender hands over responsibility to recipient.
Up to then, any failure is the sender's fault.
Beyond that is the recipient's fault.
Contracting someone else for each side does not change that reality.
As I say, there is always some technical edge cases on that specific SMTP connection, which is unavoidable but really not going to happen in most cases.
This also fixes the date/time.