Below is a list of status codes that your list can contain:

Pending – emails that have not been sent yet.
Delivered – valid email addresses that were accepted by the mail server without any issues.
Timed Out – this occurs when the mail server does not respond with a certain time period.  It varies between five seconds and thirty seconds based on your package size.  The system automatically retries timed out addresses a couple of times to be sure.
Blocked – the mail server rejected the email message. It could be based on other factors including IP reputation, subject/message content, sending too often to that address and more.
Mailbox Full – the mail server reported that the user’s quota was full and could not accept the email message.
Unknown – the mail server responded with a code that did not fit with any of the groups above.
CatchAll – A catch-all email account is an address that is specified to receive all messages that are addressed to an incorrect email address for a domain  Can be risky to mail to.

Server Not Found/Bad DNS/MX – the system was not able to connect to the mail server for that domain for the email address.
Address does not exist/Bad Address – the mail server responded with a code that indicates the email address is no longer valid.
Bad Syntax – the email address is not formatted correctly.

Settings Rejected – emails rejected on list import based on the list import settings for the account. Found Under Email Marketing -> System Settings -> List Import Settings
Optout – the user has unsubscribed from your mailings

Parking Page/Site – Domains with no content/parked at a domain parking site.
Suppressed Role – these emails match a pattern that we disallow mailing to such as abuse@ spam@
Suppressed Domain – are emails that are on our global domain suppression system and can not be mailed to
Suppressed User – are emails that are on our global user suppression system and can not be mailed to.
Suppressed Local Bounce – is a local bounce from your account from one of your lists that you had run a campaign to and the address came back as invalid.
Suppressed Bounce/Suppressed Global Bounce – is an invalid email address that is automatically detected and is based on other accounts in our system that have mailed to an address that was marked as invalid.
Suppressed Spam Bots – Spam email accounts from stopforumspam

Active Emails – consist of emails with the status of PendingDeliveredTimed OutBlockedMailbox Full and unknown. These are all considered valid emails and the system will automatically mail to them each time.
Hard Bounces Emails – consists of emails with the following status codes Server not FoundAddress does not existBad Syntax. The system will never send to emails with an inactive status code.
Suppressed emails – consists of emails with the following status codes Optout, Suppressed Role, Suppressed Domain, and Suppressed User