Receiving warning event 1021 from MSExchangeTransport on Exchange 2010

You may experience following warning message on your Exchange 2010 HUB transport servers :

Receive connector <receive connector name> rejected an incoming connection from IP address a.b.c.d. The maximum number of connections per source (20) for this connector has been reached by this source IP address.

Receive connectors has parameter that specifies maximum number of inbound connections that receive connector serves at the same time from single IP address. You can change this value by using set-receiveconnector cmdlet (for example to set this parameter to 50 concurrent connections from same IP address:  set-receiveconnector "unique receive connector name" -MaxInboundConnectionPerSource 50 ). More on set-receiveconnector http://technet.microsoft.com/en-us/library/bb125140.aspx .