diff --git a/mail/config/mozconfigs/win32/debug b/mail/config/mozconfigs/win32/debug
index 0caac35895..4bf8b56135 100644
--- a/mail/config/mozconfigs/win32/debug
+++ b/mail/config/mozconfigs/win32/debug
@@ -29,3 +29,6 @@ mk_export_correct_style INCLUDE
 # Run client.py
 mk_add_options CLIENT_PY_ARGS="$([ -f $topsrcdir/build/client.py-args ] && cat $topsrcdir/build/client.py-args)"
 mk_add_options ALWAYS_RUN_CLIENT_PY=1
+
+# Use the TOOLTOOL provided xz for mar generation.
+mk_add_options "export XZ=$TOOLTOOL_DIR/xz/xz.exe"
diff --git a/mail/config/mozconfigs/win32/l10n-mozconfig b/mail/config/mozconfigs/win32/l10n-mozconfig
index e5d1f44c39..77b80a9f1b 100644
--- a/mail/config/mozconfigs/win32/l10n-mozconfig
+++ b/mail/config/mozconfigs/win32/l10n-mozconfig
@@ -30,3 +30,6 @@ mk_export_correct_style INCLUDE
 # Run client.py
 mk_add_options CLIENT_PY_ARGS="$([ -f $topsrcdir/build/client.py-l10n-args ] && cat $topsrcdir/build/client.py-l10n-args)"
 mk_add_options ALWAYS_RUN_CLIENT_PY=1
+
+# Use the TOOLTOOL provided xz for mar generation.
+mk_add_options "export XZ=$TOOLTOOL_DIR/xz/xz.exe"
diff --git a/mail/config/mozconfigs/win32/nightly b/mail/config/mozconfigs/win32/nightly
index 278e052202..43a728bd3d 100644
--- a/mail/config/mozconfigs/win32/nightly
+++ b/mail/config/mozconfigs/win32/nightly
@@ -33,3 +33,6 @@ mk_export_correct_style INCLUDE
 # Run client.py
 mk_add_options CLIENT_PY_ARGS="$([ -f $topsrcdir/build/client.py-args ] && cat $topsrcdir/build/client.py-args)"
 mk_add_options ALWAYS_RUN_CLIENT_PY=1
+
+# Use the TOOLTOOL provided xz for mar generation.
+mk_add_options "export XZ=$TOOLTOOL_DIR/xz/xz.exe"
diff --git a/mail/config/mozconfigs/win32/release b/mail/config/mozconfigs/win32/release
index 41694e61d3..6dcf78e9bb 100644
--- a/mail/config/mozconfigs/win32/release
+++ b/mail/config/mozconfigs/win32/release
@@ -33,3 +33,6 @@ mk_export_correct_style INCLUDE
 # Run client.py
 mk_add_options CLIENT_PY_ARGS="$([ -f $topsrcdir/build/client.py-args ] && cat $topsrcdir/build/client.py-args)"
 mk_add_options ALWAYS_RUN_CLIENT_PY=1
+
+# Use the TOOLTOOL provided xz for mar generation.
+mk_add_options "export XZ=$TOOLTOOL_DIR/xz/xz.exe"
diff --git a/mail/config/mozconfigs/win64/debug b/mail/config/mozconfigs/win64/debug
index f104391db6..0045d89427 100644
--- a/mail/config/mozconfigs/win64/debug
+++ b/mail/config/mozconfigs/win64/debug
@@ -29,3 +29,6 @@ mk_export_correct_style INCLUDE
 # Run client.py
 mk_add_options CLIENT_PY_ARGS="$([ -f $topsrcdir/build/client.py-args ] && cat $topsrcdir/build/client.py-args)"
 mk_add_options ALWAYS_RUN_CLIENT_PY=1
+
+# Use the TOOLTOOL provided xz for mar generation.
+mk_add_options "export XZ=$TOOLTOOL_DIR/xz/xz.exe"
diff --git a/mail/config/mozconfigs/win64/l10n-mozconfig b/mail/config/mozconfigs/win64/l10n-mozconfig
index bba0f4b214..91cc3e2004 100644
--- a/mail/config/mozconfigs/win64/l10n-mozconfig
+++ b/mail/config/mozconfigs/win64/l10n-mozconfig
@@ -29,3 +29,6 @@ mk_export_correct_style INCLUDE
 # Run client.py
 mk_add_options CLIENT_PY_ARGS="$([ -f $topsrcdir/build/client.py-args ] && cat $topsrcdir/build/client.py-args)"
 mk_add_options ALWAYS_RUN_CLIENT_PY=1
+
+# Use the TOOLTOOL provided xz for mar generation.
+mk_add_options "export XZ=$TOOLTOOL_DIR/xz/xz.exe"
diff --git a/mail/config/mozconfigs/win64/nightly b/mail/config/mozconfigs/win64/nightly
index c57c5f324e..16dea90f3f 100644
--- a/mail/config/mozconfigs/win64/nightly
+++ b/mail/config/mozconfigs/win64/nightly
@@ -33,3 +33,6 @@ mk_export_correct_style INCLUDE
 # Run client.py
 mk_add_options CLIENT_PY_ARGS="$([ -f $topsrcdir/build/client.py-args ] && cat $topsrcdir/build/client.py-args)"
 mk_add_options ALWAYS_RUN_CLIENT_PY=1
+
+# Use the TOOLTOOL provided xz for mar generation.
+mk_add_options "export XZ=$TOOLTOOL_DIR/xz/xz.exe"