Mail Feature By Anyone ??

[greep%su-dsn at sri-unix.UUCP]

Re your question about having the sender of a message notified when the
recipient reads it: this can be trickier than it sounds.  For example, if
the recipient's secretary reads the message, does that count?  How about if
a program reads it (eg sometimes someone will set up a program to send out
a form reply saying "I'm out of town so don't expect a reply this week").
What if the recipient doesn't want you to know whether he's read it or not?
The most surefire way is probably to have a command in the the recipient's
mail system that lets him easily generate a reply saying "I've seen your
message about ...".  (You have to make sure this doesn't cause a loop by
having these things reply to each other.)

Further discussion along these lines probably belongs on MsgGroup, where
I think the subject has been discussed already.

By the way, your message mentions "the mailer" as if there were only
one mailer on Unix, which is not true.