diff --git a/bspwm/external_rules b/bspwm/external_rules
new file mode 100644
index 0000000..ff8c21b
--- /dev/null
+++ b/bspwm/external_rules
@@ -0,0 +1,11 @@
+#!/bin/sh
+
+wid=$1
+class=$2
+instance=$3
+
+echo "$wid|$class|$instance" >> ~/tmp/rules.log
+
+if [ "$instance" = Mutt ] ; then
+    echo 'desktop=^9'
+fi