You can specify the minimum queue size required to open a link to another system. The MTA queues messages until the threshold is reached, and then sends all messages in the queue. You may want to use this feature if establishing a connection is costly compared to sending data over the link.
You can specify the threshold by the number of messages in the queue, total queue size in kilobytes, or both. If you specify both thresholds, all messages in the queue are sent when either threshold is reached. You can also specify to send urgent (high importance) messages immediately.
Note This does not override the schedule specified on the Schedule property page of a connector.
You specify thresholds by setting a registry key for each link on each Microsoft Exchange Server computer you want to use thresholds on. Create the following DWORD registry keys and then modify them. Substitute the display name of the connector in upper case letters for <CONNECTOR NAME>.
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\MSExchangeMTA\Parameters\<CONNECTOR NAME >\Content Length Threshold (KBytes)
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\MSExchangeMTA\Parameters\<CONNECTOR NAME >\Queue Length Threshold
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\MSExchangeMTA\Parameters\<CONNECTOR NAME >\Urgent Overrides Thresholds
To allow urgent messages to be sent immediately, set the value of the Urgent Overrides Thresholds key to 1.