diff --git a/.config/niri/dms/windowrules.kdl b/.config/niri/dms/windowrules.kdl
new file mode 100644
index 0000000..8346fb8
--- /dev/null
+++ b/.config/niri/dms/windowrules.kdl
@@ -0,0 +1,9 @@
+// DMS Window Rules - Managed by DankMaterialShell
+// Do not edit manually - changes may be overwritten
+
+// @id=wr_1771852176240813062 @name=org.mozilla.Thunderbird
+window-rule {
+    match app-id="^org.mozilla.Thunderbird$"
+    open-maximized true
+    open-on-workspace "chat"
+}
\ No newline at end of file