To change the signature that MMDF uses when notifying senders of mail delivery problems, you must login as mmdf and edit /usr/mmdf/mmdftailor. Add a line (anywhere in the file) defining text for the MSIG parameter. The message you define should indicate which mail routing system was responsible.
For example:
MSIG "MMDF Mail System"With this definition, when users receive failed mail messages from MMDF, the message appears to be from ``MMDF Mail System''.