mailbox(8) on Linux
The text 9e64432787e2, as Debian 2.2 (Potato) shipped it.
zmailer local delivery transport agent
Flags it lists
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-8 -
-C -
-D -
-M -
-P -
-S -
-V -
-X -
-a -
-b -
-c -
-h -
-l -
-r