A long time ago, I sent a wishlist bug report about [[http://www.mutt.org/][Mutt]] for support 
of virtual folders:

  [[http://bugs.guug.de/db/68/680.html][680: Opening/searching several folders at once]]
  Package: mutt; Severity: wishlist; Reported by: Hugo Haas <hugo@larve.net>; 689 days old.

I have [[http://marc.theaimsgroup.com/?l=mutt-dev&m=105735320415174&w=2][discovered today]] that it is possible with an external program: [[http://www.rc0.org.uk/mairix][Mairix]].

Since I have two sets of folders and need to index them before doing a search, I have written a script to do so:

<example>
#! /bin/sh
#
# Usage: mairix-index (mail|private-mail) ...
#
# (c) 2003 Hugo Haas http://larve.net/people/hugo/
# Created 5 July 2003

MAIRIX=mairix
RM=/bin/rm

if [ $# -lt 1 ]; then
  exit 1
fi

TEMPCONF=/tmp/mairixrc-temp-hh.$$
trap "$RM -f $TEMPCONF; exit" 0 1 2 3 15

cat << EOF > $TEMPCONF
base=$HOME/$1
database=$HOME/.mairix_index_$1
vfolder=archives/vfolder
EOF
echo "folders=`ls $HOME/$1 | grep -v -F 'archives/' | tr -d / | xargs echo | tr \  :`" >> $TEMPCONF
shift
echo "Created $TEMPCONF as a mairixrc:"
cat $TEMPCONF

echo "Updating index"
$MAIRIX -f $TEMPCONF -p

echo "Running mairix search:"
$MAIRIX -f $TEMPCONF -v "$@"
</example>

Then, from Mutt, I have macros to to do a search and see the results:
<example>
##########################################################################
# Virtual folders: mairix

  macro index \eM "<shell-escape>$HOME/.mutt/mairix-index BASE " "Run a Mairix search"
  macro index \eF "<change-folder-readonly>=archives/vfolder/\n" "Switch to Mairix virtual folder"
</example>

Note: =BASE= is either =mail= or =private-mail= and is set with my [[../../2002/04/mutt-cpp.html][M4 muttrc preprocessing]].

Then, I can a search for "Hugo" with *\eM Hugo* and then see the results with *\eF*.

Hella cool!