diff --git a/src/pretix/api/views/checkin.py b/src/pretix/api/views/checkin.py
index d5896b1ee8..75c98bc4a2 100644
--- a/src/pretix/api/views/checkin.py
+++ b/src/pretix/api/views/checkin.py
@@ -258,11 +258,13 @@ class CheckinListPositionViewSet(viewsets.ReadOnlyModelViewSet):
         except CheckInError as e:
             return Response({
                 'status': 'error',
-                'reason': e.code
+                'reason': e.code,
+                'data': OrderPositionSerializer(op).data
             }, status=400)
         else:
             return Response({
                 'status': 'ok',
+                'data': OrderPositionSerializer(op).data
             }, status=201)
 
     def get_object(self):
diff --git a/src/pretix/base/services/mail.py b/src/pretix/base/services/mail.py
index 83aacf72b6..529b369ef3 100644
--- a/src/pretix/base/services/mail.py
+++ b/src/pretix/base/services/mail.py
@@ -1,4 +1,5 @@
 import logging
+import smtplib
 from email.utils import formataddr
 from typing import Any, Dict, List, Union
 
@@ -170,8 +171,8 @@ def mail(email: str, subject: str, template: Union[str, LazyI18nString],
         chain(*task_chain).apply_async()
 
 
-@app.task
-def mail_send_task(*args, to: List[str], subject: str, body: str, html: str, sender: str,
+@app.task(bind=True)
+def mail_send_task(self, *args, to: List[str], subject: str, body: str, html: str, sender: str,
                    event: int=None, headers: dict=None, bcc: List[str]=None, invoices: List[int]=None,
                    order: int=None, attach_tickets=False) -> bool:
     email = EmailMultiAlternatives(subject, body, sender, to=to, bcc=bcc, headers=headers)
@@ -219,7 +220,34 @@ def mail_send_task(*args, to: List[str], subject: str, body: str, html: str, sen
 
     try:
         backend.send_messages([email])
-    except Exception:
+    except smtplib.SMTPResponseException as e:
+        if e.smtp_code in (101, 111, 421, 422, 431, 442, 447, 452):
+            self.retry(max_retries=5, countdown=2 ** (self.request.retries * 2))
+        logger.exception('Error sending email')
+
+        if order:
+            order.log_action(
+                'pretix.event.order.email.error',
+                data={
+                    'subject': 'SMTP code {}'.format(e.smtp_code),
+                    'message': e.smtp_error.decode() if isinstance(e.smtp_error, bytes) else str(e.smtp_error),
+                    'recipient': '',
+                    'invoices': [],
+                }
+            )
+
+        raise SendMailException('Failed to send an email to {}.'.format(to))
+    except Exception as e:
+        if order:
+            order.log_action(
+                'pretix.event.order.email.error',
+                data={
+                    'subject': 'Internal error',
+                    'message': str(e),
+                    'recipient': '',
+                    'invoices': [],
+                }
+            )
         logger.exception('Error sending email')
         raise SendMailException('Failed to send an email to {}.'.format(to))
 
diff --git a/src/pretix/control/logdisplay.py b/src/pretix/control/logdisplay.py
index ab2152c112..2c5687ef51 100644
--- a/src/pretix/control/logdisplay.py
+++ b/src/pretix/control/logdisplay.py
@@ -187,6 +187,7 @@ def pretixcontrol_logentry_display(sender: Event, logentry: LogEntry, **kwargs):
                                                   'toggled.'),
         'pretix.event.order.payment.changed': _('A new payment {local_id} has been started instead of the previous one.'),
         'pretix.event.order.email.sent': _('An unidentified type email has been sent.'),
+        'pretix.event.order.email.error': _('Sending of an email has failed.'),
         'pretix.event.order.email.custom_sent': _('A custom email has been sent.'),
         'pretix.event.order.email.download_reminder_sent': _('An email has been sent with a reminder that the ticket '
                                                              'is available for download.'),