diff --git a/core/admin/mailu/models.py b/core/admin/mailu/models.py
index 48b47ea5..88223cf7 100644
--- a/core/admin/mailu/models.py
+++ b/core/admin/mailu/models.py
@@ -258,6 +258,7 @@ class Domain(Base):
             ('submission', 587),
             ('imap', 143),
             ('pop3', 110),
+            ('autodiscover', 443),
         ]
         if app.config['TLS_FLAVOR'] != 'notls':
             protocols.extend([