If you send an email via their email address and you activate the "read receipt", you will know if the person has read your email. If it's an incorrect email address, you will get an 'undeliverable message'.
If you send an email via SFI's email, then you can go to your sent items and if your email is in 'bold', it has not been read. If it's 'unbolded', your message has been read.
I hope this has helped.
