diff --git a/addons/mail/static/src/components/chat_window_manager/chat_window_manager.scss b/addons/mail/static/src/components/chat_window_manager/chat_window_manager.scss
index 1e8abf54184..4bf512a6603 100644
--- a/addons/mail/static/src/components/chat_window_manager/chat_window_manager.scss
+++ b/addons/mail/static/src/components/chat_window_manager/chat_window_manager.scss
@@ -3,14 +3,5 @@
 // ------------------------------------------------------------------
 
 .o_ChatWindowManager {
-    bottom: 0;
-    right: 0;
-    display: flex;
-    flex-direction: row-reverse;
-    z-index: 1000;
+    z-index: $zindex-dropdown;
 }
-
-// ------------------------------------------------------------------
-// Style
-// ------------------------------------------------------------------
-
diff --git a/addons/mail/static/src/components/chat_window_manager/chat_window_manager.xml b/addons/mail/static/src/components/chat_window_manager/chat_window_manager.xml
index 52b6a340795..e8d57227d7a 100644
--- a/addons/mail/static/src/components/chat_window_manager/chat_window_manager.xml
+++ b/addons/mail/static/src/components/chat_window_manager/chat_window_manager.xml
@@ -2,7 +2,7 @@
 <templates xml:space="preserve">
 
     <t t-name="mail.ChatWindowManager" owl="1">
-        <div class="o_ChatWindowManager" t-attf-class="{{ className }}" t-ref="root">
+        <div class="o_ChatWindowManager flex-row-reverse d-flex" t-attf-class="{{ className }}" t-ref="root">
             <t t-if="messaging and messaging.chatWindowManager">
                 <!-- Note: DOM elements are ordered from left to right -->
                 <t t-if="messaging.chatWindowManager.hasHiddenChatWindows">