diff --git a/addons/mail/models/mail_activity.py b/addons/mail/models/mail_activity.py
index f5904c772a3..8be9c6abf71 100644
--- a/addons/mail/models/mail_activity.py
+++ b/addons/mail/models/mail_activity.py
@@ -244,27 +244,32 @@ class MailActivity(models.Model):
         is to allow assigned user to handle their activities. For that purpose
         assigned user should be able to at least read the document. We therefore
         raise an UserError if the assigned user has no access to the document. """
-        for activity in self:
-            model = self.env[activity.res_model].with_user(activity.user_id).with_context(allowed_company_ids=activity.user_id.company_ids.ids)
-            try:
-                model.check_access_rights('read')
-            except exceptions.AccessError:
-                raise exceptions.UserError(
-                    _('Assigned user %s has no access to the document and is not able to handle this activity.',
-                      activity.user_id.display_name))
-            else:
+        for model, activity_data in self._classify_by_model().items():
+            # group activities / user, in order to batch the check of ACLs
+            per_user = dict()
+            for activity in activity_data['activities'].filtered(lambda act: act.user_id):
+                if activity.user_id not in per_user:
+                    per_user[activity.user_id] = activity
+                else:
+                    per_user[activity.user_id] += activity
+            for user, activities in per_user.items():
+                RecordModel = self.env[model].with_user(user).with_context(
+                    allowed_company_ids=user.company_ids.ids
+                )
                 try:
-                    target_user = activity.user_id
-                    target_record = self.env[activity.res_model].browse(activity.res_id)
-                    if hasattr(target_record, 'company_id') and (
-                        target_record.company_id != target_user.company_id and (
-                            len(target_user.sudo().company_ids) > 1)):
-                        return  # in that case we skip the check, assuming it would fail because of the company
-                    model.browse(activity.res_id).check_access_rule('read')
+                    RecordModel.check_access_rights('read')
                 except exceptions.AccessError:
                     raise exceptions.UserError(
                         _('Assigned user %s has no access to the document and is not able to handle this activity.',
-                          activity.user_id.display_name))
+                          user.display_name))
+                else:
+                    try:
+                        target_records = self.env[model].browse(activities.mapped('res_id'))
+                        target_records.check_access_rule('read')
+                    except exceptions.AccessError:
+                        raise exceptions.UserError(
+                            _('Assigned user %s has no access to the document and is not able to handle this activity.',
+                              user.display_name))
 
     # ------------------------------------------------------
     # ORM overrides