mail(1) on OpenBSD
The text d1dfc6db2370, as OpenBSD 6.8, OpenBSD 6.7, OpenBSD 6.6 shipped it.
send and receive mail
Flags it lists
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-E -
-I -
-N -
-b -
-c -
-d -
-f -
-i -
-n -
-r -
-s -
-u -
-v