Answer
GMS will accept a message from a robot or executable and automatically queue it for delivery. It will accept the message on STDOUT and look for the To:, CC: and BCC: clauses (the latter will be removed automatically by GMS). The number of destinations requested by the robot was too high so any over the maximum will be ignored.
In this case session Undefined was processing a message from a server/client at Undefined apparently from Undefined to Undefined. The robot was executed and produced an email message with Undefined recipients which is over the maximum of Undefined recipients.
This is the correct result, this is not an error within GMS. The robot will need to be modified not to produce so many recipients.
See Also:
Keywords:robot recipients CC BCC To 8260