Answer
A robot domain is a special type of domain that allows an executable to be run on receipt of mail to the domain. Mail sent to any usr at the domain will cause the associated executable file to be run. This executable file could potentially do anything you wished, but one common usage would be to re-write the domain portion of the recipient email address to point to another domain. A robot domain does not require an IP address.
You can give the executable access to the e-mail contents via the standard input and output streams if the "Send message to Robot" and/or "Accept message from Robot" check boxes are selected. For example code for an executable program, see "Robots" in the GMS Reference Guide.
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Keywords:robot, domain, mailbox, processing, process, executable