fdm(1) on Linux
The text c892d3708fc5, as Debian 9 (Stretch), Debian 8 (Jessie), Debian 7 (Wheezy), Debian 6.0 (Squeeze) shipped it.
fetch and deliver mail
Flags it lists
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-D -
-a -
-f -
-h -
-k -
-l -
-m -
-n -
-q -
-u -
-v -
-x