Messaging Queues have a set of conditions that can define which queue items will be dispatched, out of the already stored list.
By clicking on the Conditions item, you should see the following form:
Messaging Queue conditions are used to filter out the list of queue items so that you can send the questionnaire only to a specific set of recipients, that match the selected conditions.
You can choose your conditions to be metadata, either questionnaire or responder.
Pipeline conditions are easy to use in cases where you need to push all your recipients into one list and then select which ones to send, given the selected conditions.
Any items that do not match the conditions will be skipped with the status Ignored. This will prevent the pipeline from dispatching the items when the conditions change.