smtp-sink(1) on macOS
The text cb76f8e6f39a, as Mac OS X 10.3.9, Mac OS X 10.3.8, Mac OS X 10.3.7, Mac OS X 10.3.6, Mac OS X 10.3.5, Mac OS X 10.3.4, Mac OS X 10.3.3, Mac OS X 10.3.2, Mac OS X 10.3.1, Mac OS X 10.3 shipped it.
multi-threaded SMTP/LMTP test server
Flags it lists
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-8 -
-L -
-P -
-c -
-e -
-h -
-n -
-p -
-s -
-v -
-w