Index: thunderbird.in
===================================================================
--- thunderbird.in (nonexistent)
+++ thunderbird.in (revision 173)
@@ -0,0 +1,9 @@
+#!/bin/sh
+#
+# Shell script to start Mozilla Thunderbird.
+#
+# Don't reset the user profile on a detected downgrade:
+export MOZ_ALLOW_DOWNGRADE=1
+
+# Start Thunderbird:
+exec /usr/lib@LIBDIRSUFFIX@/thunderbird/thunderbird "$@"