/usr/share/mailutils/mh/replgroupcomps is in mailutils-mh 1:2.99.99-1ubuntu2.
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 | %; This is the default replgroupcomps file for Mailutils MH.
%;
%; GNU Mailutils -- a suite of utilities for electronic mail
%; Copyright (C) 2003, 2010-2012, 2014-2015 Free Software Foundation,
%; Inc.
%; Distributed under GPL.
%;
%(lit)%(formataddr{mail-followup-to})\
%<(nonnull)%(void(width))%(putaddr To: )\n\
%|\
%(lit)%(formataddr %<{mail-reply-to}%?{reply-to}%?{from}%?{sender}%?{return-path}%>)\
%<(nonnull)%(void(width))%(putaddr To: )\n%>\
%(lit)%<(rcpt to)%(formataddr{to})%>%<(rcpt cc)%(formataddr{cc})%>%<(rcpt me)%(formataddr(me))%>\
%<(nonnull)%(void(width))%(putaddr cc: )\n%>%>\
%;
%<(mymbox{from})%<{fcc}Fcc: %{fcc}\n%>%>\
%<{subject}%(lit)%<(isreply{subject})%?(profile reply-prefix)%(concat)%|%(concat Re:)%>%(concat{subject})%(printhdr Subject: )\n%>\
%(lit)%(concat(in_reply_to))%<(nonnull)%(void(width))%(printhdr In-reply-to: )\n%>\
%(lit)%(concat(references))%<(nonnull)%(void(width))%(printhdr References: )\n%>\
--------
|