Mail read by delegate

I have seen some machines in our organisations which inform the user if a delegate has read an email. For the life of me I cant track down how to activate this setting. it would be really useful if I know that someone in my team has read a mail or not. Does anyone know how to activate this function?

many thanks

Subject: Mail read by delegate

Try this link:

http://www-12.lotus.com/ldd/doc/domino_notes/Rnext/help6_client.nsf/f4b82fbb75e942a6852566ac0037f284/823ad71c36414be085256c1c0037d6f6?OpenDocument

Regards,

Litty Joseph