An I/O queue is a list of messages which are tagged as either incoming (received from an application) or outgoing (going to an application).  Incoming messages are processed and converted into outgoing messages. An incoming message is placed on the I/O Queue by a Receive Port, and when the I/O Queue is sending a message it is placed on the Send Port. Both receive and send ports are managed by the I/O Queue Transport.  (Web Services can also handle messages instead of using send and receive ports.)

I/O Queues can have forms and columns, which can be seen in the Blue Integrator Explorer, but these forms and columns are usually used for connectivity to applications such as Outlook and SharePoint, which prefer these formats.

One of the major advantages of using I/O Queues is that they can be manipulated from outside Blue Integrator. The most common example is exposing the I/O Queue as a Web service. Messages can, as mentioned above, be synchronized with Outlook and SharePoint (as well as other application) which still on the I/O Queue.  In these cases, an incoming message to the I/O Queue can be synchronized with an item (such as an Outlook task or a SharePoint list) which can view and even edit the message while on the I/O Queue. For information on synchronizing Blue Integrator I/O Queues, see Outlook Integration and SharePoint Integration.