smtp-source(1) on macOS
The text f9dfe1b59294, as Mac OS X 10.5.8, Mac OS X 10.5.7, Mac OS X 10.5.6, Mac OS X 10.5.5, Mac OS X 10.5.4, Mac OS X 10.5.3, Mac OS X 10.5.2, Mac OS X 10.5.1, Mac OS X 10.5 shipped it.
multi-threaded SMTP/LMTP test generator
Flags it lists
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-4 -
-6 -
-C -
-L -
-M -
-N -
-R -
-S -
-c -
-d -
-f -
-l -
-m -
-o -
-r -
-s -
-t -
-v -
-w