diff --git a/addons/mail/models/ir_model.py b/addons/mail/models/ir_model.py
index d2a296e6849..30084eb1a7b 100644
--- a/addons/mail/models/ir_model.py
+++ b/addons/mail/models/ir_model.py
@@ -20,26 +20,35 @@ class IrModel(models.Model):
     )
 
     def unlink(self):
+        """ Delete mail data (followers, messages, activities) associated with
+        the models being deleted.
+        """
         if not self:
             return True
 
         # Delete followers, messages and attachments for models that will be unlinked.
+        mail_models = self.search([
+            ('model', 'in', ('mail.activity', 'mail.activity.type', 'mail.followers', 'mail.message'))
+        ], order='id')
+
+        if not (self & mail_models):
+            models = tuple(self.mapped('model'))
+            model_ids = tuple(self.ids)
+
+            query = "DELETE FROM mail_activity WHERE res_model_id IN %s"
+            self.env.cr.execute(query, [model_ids])
+
+            query = "DELETE FROM mail_activity_type WHERE res_model IN %s"
+            self.env.cr.execute(query, [models])
+
+            query = "DELETE FROM mail_followers WHERE res_model IN %s"
+            self.env.cr.execute(query, [models])
+
+            query = "DELETE FROM mail_message WHERE model in %s"
+            self.env.cr.execute(query, [models])
+
+        # Get files attached solely to the models being deleted (and none other)
         models = tuple(self.mapped('model'))
-        model_ids = tuple(self.ids)
-
-        query = "DELETE FROM mail_activity WHERE res_model_id IN %s"
-        self.env.cr.execute(query, [model_ids])
-
-        query = "DELETE FROM mail_activity_type WHERE res_model IN %s"
-        self.env.cr.execute(query, [models])
-
-        query = "DELETE FROM mail_followers WHERE res_model IN %s"
-        self.env.cr.execute(query, [models])
-
-        query = "DELETE FROM mail_message WHERE model in %s"
-        self.env.cr.execute(query, [models])
-
-        # Get files attached solely by the models
         query = """
             SELECT DISTINCT store_fname
             FROM ir_attachment