/etc/apparmor.d/abstractions/user-mail is in apparmor 2.12-4ubuntu5.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 | # ------------------------------------------------------------------
#
# Copyright (C) 2002-2006 Novell/SUSE
# Copyright (C) 2014 Canonical Ltd.
#
# This program is free software; you can redistribute it and/or
# modify it under the terms of version 2 of the GNU General Public
# License published by the Free Software Foundation.
#
# ------------------------------------------------------------------
# location of user mail, spool and mboxes
owner @{HOME}/[mM]ail/ r,
owner @{HOME}/[mM]ail/** rwl,
owner @{HOME}/postponed* rwl,
/var/{,spool/}mail/ r,
owner /var/{,spool/}mail/* rwl,
owner @{HOME}/mbox.lock* rwl,
owner @{HOME}/mbox rw,
owner @{HOME}/inbox rw,
owner @{HOME}/.forward r,
owner @{HOME}/Maildir/ r,
owner @{HOME}/Maildir/** rwl,
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