diff --git a/addons/mass_mailing/models/mass_mailing.py b/addons/mass_mailing/models/mass_mailing.py
index ae15fab41c0..b3a8958ff55 100644
--- a/addons/mass_mailing/models/mass_mailing.py
+++ b/addons/mass_mailing/models/mass_mailing.py
@@ -153,7 +153,7 @@ class MassMailingCampaign(models.Model):
     mass_mailing_ids = fields.One2many(
         'mail.mass_mailing', 'mass_mailing_campaign_id',
         string='Mass Mailings')
-    unique_ab_testing = fields.Boolean(string='Allow A/B Testing', default=True,
+    unique_ab_testing = fields.Boolean(string='Allow A/B Testing', default=False,
         help='If checked, recipients will be mailed only once for the whole campaign. '
              'This lets you send different mailings to randomly selected recipients and test '
              'the effectiveness of the mailings, without causing duplicate messages.')