--- a/python/mozbuild/mozbuild/schedules.py
+++ b/python/mozbuild/mozbuild/schedules.py
@@ -41,11 +41,13 @@ EXCLUSIVE_COMPONENTS = [
     'robocop',
     'talos',
     'telemetry-tests-client',
     'xpcshell',
     'xpcshell-coverage',
     'web-platform-tests',
     'web-platform-tests-reftests',
     'web-platform-tests-wdspec',
+    # Thunderbird test suites
+    'mozmill',
 ]
 EXCLUSIVE_COMPONENTS = sorted(EXCLUSIVE_COMPONENTS)
 ALL_COMPONENTS = INCLUSIVE_COMPONENTS + EXCLUSIVE_COMPONENTS