'In writing'...email? sms? what have you been told?

[s_t]

and isn't this all dependant on them using an email program, and having the settings set to send such things.

I use evolution (linux) and have send receipts set as 'never' (which is the default settting I think). I don't know why anyone would allow information to be sent off about when they read a particular email, especially before they even know what is in it. Kind of like giving everyone open permission to monitor/spy on you.....