--- a/mail/config/mozconfigs/win32/debug
+++ b/mail/config/mozconfigs/win32/debug
@@ -24,8 +24,11 @@ export MOZ_PACKAGE_JSSHELL=1
 
 # Set up mapi includes (must be done after visual studio setup)
 export INCLUDE=$INCLUDE:/c/Office\ 2010\ Developer\ Resources/Outlook\ 2010\ MAPI\ Headers
 mk_export_correct_style INCLUDE
 
 # Run client.py
 mk_add_options CLIENT_PY_ARGS="$([ -f $topsrcdir/build/client.py-args ] && cat $topsrcdir/build/client.py-args)"
 mk_add_options ALWAYS_RUN_CLIENT_PY=1
+
+# Use the TOOLTOOL provided xz for mar generation.
+XZ="$TOOLTOOL_DIR/xz/xz.exe"

--- a/mail/config/mozconfigs/win32/l10n-mozconfig
+++ b/mail/config/mozconfigs/win32/l10n-mozconfig
@@ -25,8 +25,11 @@ MOZ_REQUIRE_ADDON_SIGNING=0
 
 # Set up mapi includes (must be done after visual studio setup)
 export INCLUDE=$INCLUDE:/c/Office\ 2010\ Developer\ Resources/Outlook\ 2010\ MAPI\ Headers
 mk_export_correct_style INCLUDE
 
 # Run client.py
 mk_add_options CLIENT_PY_ARGS="$([ -f $topsrcdir/build/client.py-l10n-args ] && cat $topsrcdir/build/client.py-l10n-args)"
 mk_add_options ALWAYS_RUN_CLIENT_PY=1
+
+# Use the TOOLTOOL provided xz for mar generation.
+XZ="$TOOLTOOL_DIR/xz/xz.exe"

--- a/mail/config/mozconfigs/win32/nightly
+++ b/mail/config/mozconfigs/win32/nightly
@@ -28,8 +28,11 @@ export MOZ_PACKAGE_JSSHELL=1
 
 # Set up mapi includes (must be done after visual studio setup)
 export INCLUDE=$INCLUDE:/c/Office\ 2010\ Developer\ Resources/Outlook\ 2010\ MAPI\ Headers
 mk_export_correct_style INCLUDE
 
 # Run client.py
 mk_add_options CLIENT_PY_ARGS="$([ -f $topsrcdir/build/client.py-args ] && cat $topsrcdir/build/client.py-args)"
 mk_add_options ALWAYS_RUN_CLIENT_PY=1
+
+# Use the TOOLTOOL provided xz for mar generation.
+XZ="$TOOLTOOL_DIR/xz/xz.exe"

--- a/mail/config/mozconfigs/win32/release
+++ b/mail/config/mozconfigs/win32/release
@@ -28,8 +28,11 @@ export MOZ_PACKAGE_JSSHELL=1
 
 # Set up mapi includes (must be done after visual studio setup)
 export INCLUDE=$INCLUDE:/c/Office\ 2010\ Developer\ Resources/Outlook\ 2010\ MAPI\ Headers
 mk_export_correct_style INCLUDE
 
 # Run client.py
 mk_add_options CLIENT_PY_ARGS="$([ -f $topsrcdir/build/client.py-args ] && cat $topsrcdir/build/client.py-args)"
 mk_add_options ALWAYS_RUN_CLIENT_PY=1
+
+# Use the TOOLTOOL provided xz for mar generation.
+XZ="$TOOLTOOL_DIR/xz/xz.exe"

--- a/mail/config/mozconfigs/win64/debug
+++ b/mail/config/mozconfigs/win64/debug
@@ -24,8 +24,11 @@ MOZ_REQUIRE_ADDON_SIGNING=0
 
 # Set up mapi includes (must be done after visual studio setup)
 export INCLUDE=$INCLUDE:/c/Office\ 2010\ Developer\ Resources/Outlook\ 2010\ MAPI\ Headers
 mk_export_correct_style INCLUDE
 
 # Run client.py
 mk_add_options CLIENT_PY_ARGS="$([ -f $topsrcdir/build/client.py-args ] && cat $topsrcdir/build/client.py-args)"
 mk_add_options ALWAYS_RUN_CLIENT_PY=1
+
+# Use the TOOLTOOL provided xz for mar generation.
+XZ="$TOOLTOOL_DIR/xz/xz.exe"

--- a/mail/config/mozconfigs/win64/l10n-mozconfig
+++ b/mail/config/mozconfigs/win64/l10n-mozconfig
@@ -24,8 +24,11 @@ MOZ_REQUIRE_ADDON_SIGNING=0
 
 # Set up mapi includes (must be done after visual studio setup)
 export INCLUDE=$INCLUDE:/c/Office\ 2010\ Developer\ Resources/Outlook\ 2010\ MAPI\ Headers
 mk_export_correct_style INCLUDE
 
 # Run client.py
 mk_add_options CLIENT_PY_ARGS="$([ -f $topsrcdir/build/client.py-args ] && cat $topsrcdir/build/client.py-args)"
 mk_add_options ALWAYS_RUN_CLIENT_PY=1
+
+# Use the TOOLTOOL provided xz for mar generation.
+XZ="$TOOLTOOL_DIR/xz/xz.exe"

--- a/mail/config/mozconfigs/win64/nightly
+++ b/mail/config/mozconfigs/win64/nightly
@@ -28,8 +28,11 @@ export MOZ_PACKAGE_JSSHELL=1
 
 # Set up mapi includes (must be done after visual studio setup)
 export INCLUDE=$INCLUDE:/c/Office\ 2010\ Developer\ Resources/Outlook\ 2010\ MAPI\ Headers
 mk_export_correct_style INCLUDE
 
 # Run client.py
 mk_add_options CLIENT_PY_ARGS="$([ -f $topsrcdir/build/client.py-args ] && cat $topsrcdir/build/client.py-args)"
 mk_add_options ALWAYS_RUN_CLIENT_PY=1
+
+# Use the TOOLTOOL provided xz for mar generation.
+XZ="$TOOLTOOL_DIR/xz/xz.exe"