This file is indexed.

/etc/mail.rc is in bsd-mailx 8.1.2-0.20160123cvs-4.

This file is owned by root:root, with mode 0o644.

The actual contents of the file can be viewed below.

1
2
set ask askcc append dot save crt
ignore Received Message-Id Resent-Message-Id Status Mail-From Return-Path Via Delivered-To