diff --git a/src/pretix/control/forms/filter.py b/src/pretix/control/forms/filter.py
index bec57b8476..d4e5d8b37d 100644
--- a/src/pretix/control/forms/filter.py
+++ b/src/pretix/control/forms/filter.py
@@ -2856,9 +2856,9 @@ class OutgoingMailFilterForm(FilterForm):
         if fdata.get('query'):
             query = fdata.get('query')
             qs = qs.filter(
-                Q(to__containsstring=query)
-                | Q(cc__containsstring=query)
-                | Q(bcc__containsstring=query)
+                Q(to__containsstring=query.lower())
+                | Q(cc__containsstring=query.lower())
+                | Q(bcc__containsstring=query.lower())
                 | Q(subject__icontains=query)
             )
 
diff --git a/src/tests/control/test_organizer.py b/src/tests/control/test_organizer.py
index 3dd1b45728..233cd56012 100644
--- a/src/tests/control/test_organizer.py
+++ b/src/tests/control/test_organizer.py
@@ -485,10 +485,10 @@ class OrganizerTest(SoupTest):
         assert b"rightrecipient@example.com" not in resp.content
 
         if 'postgresql' in settings.DATABASES['default']['ENGINE']:
-            resp = self.client.get('/control/organizer/%s/outgoingmails?query=rightrecipient' % self.orga1.slug)
+            resp = self.client.get('/control/organizer/%s/outgoingmails?query=RIGHTrecipient@example.com' % self.orga1.slug)
             assert resp.status_code == 200
             assert b"rightrecipient@example.com" in resp.content
-            resp = self.client.get('/control/organizer/%s/outgoingmails?query=wrongrecipient' % self.orga1.slug)
+            resp = self.client.get('/control/organizer/%s/outgoingmails?query=wrongrecipient@example.com' % self.orga1.slug)
             assert resp.status_code == 200
             assert b"rightrecipient@example.com" not in resp.content