Copy of email to goto users email address

I am looking for the following functionality.
? Four different pages with 4 different forms all to send email to four different email addresses.
? Part of each form is the entry of the users email address – I want a copy of the email address sent to the user (either pulling the address from the field that it was first entered into or by having to insert the address a second time in another field labelled “if you wish to receive a copy of this email please enter the email address here”)
Any ideas?
Thanks