If you have full access to someone else's email, can a read receipt be generated with your name - even though you never opened or previewed the email? I had this happen to me. The problem is that the read receipt was delivered to the sender of the email, they received two read receipts within ~1-minute, one from the original intender of the email and one from me (who has full access), however, again at that time I was not in the other person email.
I actually have access to another email account (same full access) and when we tested it, the read receipt was from the original account and not me (who has full access). Even after opening, unreading and reopening, we couldn't generate a read receipt.