A message can be in various states, each depicting the status of what is happening or has happened with the message. The following is a list of states that a message can be in.
Active: A message that has not been answered. It could mean that the message is open in your Inbox, but not answered, or that it is open in someone else's Inbox. A message remains active until closed by applying one of the following actions: Answer, Redirect, or No Answer.
All: To view the overall accumulated message states without categorization
Pending send: A message that is ready to be sent by the mail sender
Pending collaborate: A message that is waiting for a response from a collaborator
Pending forward track: A message that is waiting for a response from a forward and track action
Completed: A message that has been answered, not answered, or redirected