@AlanMunn -- Most mailers insert the current time when a message is sent. Assuming that isn't changed by the receiving mail system (possibly unreliable), you could ask the sender to report the time shown at
time.is/GMT and figure it out from there. If the sending time is reliable, it could probably be automated. Oh, it does depend on the mail being sent from a site local to the sender. (I'm sending/receiving mail on a machine where I'm connected by ssh, so not reliable.)