Normally the router uses one thread to for server to server mail transfer but this can be overriden by enabling this parameter so that the router will use multiple threads to the same server thereby increasing mail flow.
Use this setting to enable/disable multiple concurrent transfer threads for inter-domain Notes routing.
Valid Values are:
1 - Enables
0 - Disables
This is a new feature available for Domino 5.0.3 and gives the Domino server the ability to connect to Notes domains and transfer Notes mail over NRPC or SMTP, using multiple concurrent transfer threads. This feature works in conjunction with the "maximum concurrent transfer threads" field. This setting helps increase the number of simultaneous transfer threads used to route mail to the same domain and should assist with mail routing performance.