With a quick glance on your Stats page, you would see the following status'.
Unsent: Call sheet has not been sent to recipient.
Sent: The call sheet has been successfully delivered to recipient.
Bounced: Receiving server could not or would not accept message.
Spam: Recipient marked message as spam.
Delivered: Message has been successfully delivered to the receiving server.
Opened: Recipient received the call time email and opened it.
Confirmed: You can see who confirmed their call time with a timestamp for verification.
Blocked: When your IP address has been added to a blacklist, they have been blocked by an ISP or messaging organization, the affected email shows up with this status.
Dropped: You may see the following drop reasons: Invalid SMTPAPI header, Spam Content (if spam checker app enabled), Unsubscribed Address, Bounced Address, Spam Reporting Address, Invalid, Recipient List over Package Quota
Deferred: Recipient’s email server temporarily rejected message.