The following counters are available in the Microsoft Exchange Server Queues chart view.
| Counter | Object | Description |
| Work Queue Length | MTA | The number of messages that the MTA has not yet processed. |
| Send Queue Size | Private information store and public information store | The number of sent messages that are waiting for final delivery. |
| Receive Queue Size | Private information store and public information store | The number of received messages that are waiting for final delivery. |