Different Queues in Exchange Server 2007

• Submissions: Used by the categorizer to gather all messages that have to be resolved, routed, and processed by Transport agents.
• Poison Message: The poison message queue is a special queue that is used to isolate messages that are detected to be potentially harmful to the Exchange 2007 system after a server failure.
• Remote Delivery: Remote delivery queues hold messages that are being delivered to a remote server by using SMTP.
• Mailbox Delivery: The mailbox delivery queues hold messages that are being delivered to a mailbox server by using encrypted Exchange RPC.
• Unreachable Destination: Each transport server can have only one Unreachable queue. The Unreachable queue contains messages that cannot be routed to their destinations.