If I send an e-mail to someone, is there any way I can find out if they actually received it ( or at least it was received at the address to which it was sent)?
Yes, a lot of email packages allow you to add a "read receipt". This will let you know that the user has seen your message but only if their email package supports read reciepts and/or they choose to send you one.
if the email is not delivered for some reason, it will normally be returned to you.
i have Virgin broadband / email, i have not used that used that read /reciept but i know it is on the right hand side of the desktop, you just need to click it.
Good Luck