diff --git a/rc_hip/repapp/mail_interface.py b/rc_hip/repapp/mail_interface.py
new file mode 100644
index 0000000..a5a22ec
--- /dev/null
+++ b/rc_hip/repapp/mail_interface.py
@@ -0,0 +1,100 @@
+import os
+import re
+import logging
+from imap_tools import MailBox, AND, MailMessage
+from django.core.mail import send_mail
+from .models import Guest, Message, Question, Organisator
+
+logger = logging.getLogger(__name__)
+
+
+def send_message_notification(message: Message, guest: Guest):
+    """
+    Send new message notification.
+    """
+    organizers = []
+    for organizer in Organisator.objects.all():
+        organizers.append(organizer.mail)
+
+    subject = f'Neue Nachricht von Gast {guest.name} ({guest.mail})'
+    text = f'Hallo,\n'
+    f'der Gast {guest.name} ({guest.mail}) hat folgende Nachricht gesendet:\n\n'
+    f'{message.message}'
+    # TODO: HTML message
+    # TODO: add attachments
+    # TODO: add link to message
+
+    send_mail(
+        subject=subject,
+        message=text,
+        from_email=os.getenv("DJANGO_SENDER_ADDRESS", ""),
+        recipient_list=organizers,
+        fail_silently=True
+    )
+
+
+def process_message(message: MailMessage, guest: Guest):
+    """
+    Process a valid message from a guest.
+    """
+    content = message.text
+    if message.html:
+        content = message.html
+
+    result = re.search('Q#([0-9]+):', message.subject)
+    if result:
+        question_pk = result.group(1)
+        question = Question.objects.filter(pk=question_pk).first()
+        if question:
+            if question.device.guest.mail == message.from_:
+                question.answer = content
+                question.save()
+                # TODO: save attachments and add to message
+                logger.info(
+                    'Valid answer for Question %s from %s received.'
+                    % (question_pk, message.from_))
+                # TODO: send notifications
+            else:
+                logger.warning(
+                    'Answer for Question %s from %s received,'
+                    ' but the question was not for this guest. Message was ignored.'
+                    % (question_pk, message.from_))
+                # TODO: send reply that mail address was wrong
+        else:
+            logger.warning(
+                'Answer for Question %s from %s received,'
+                ' but there is no such question. Message was ignored.'
+                % (question_pk, message.from_))
+    else:
+        db_message = Message(
+            message=content,
+            guest=guest,
+        )
+        db_message.save()
+        send_message_notification(message, guest)
+
+
+def process_mails():
+    """
+    Check for new messages and handle valid messages.
+    """
+    host = os.getenv("DJANGO_EMAIL_HOST", "")
+    user = os.getenv("DJANGO_EMAIL_HOST_USER", None)
+    password = os.getenv("DJANGO_EMAIL_HOST_PASSWORD", None)
+    mailbox = MailBox(host).login(user, password)
+    messages = mailbox.fetch(criteria=AND(seen=False),
+                             mark_seen=True, bulk=True)
+
+    message_count = 0
+    for message in messages:
+        message_count += 1
+        sender = message.from_
+        guest = Guest.objects.filter(mail=sender).first()
+        if guest:
+            process_message(message, guest)
+        else:
+            logger.warning(
+                'Mail form unknown sender %s with subject %s ignored.'
+                % (sender, message.subject))
+
+    return message_count
diff --git a/rc_hip/repapp/views.py b/rc_hip/repapp/views.py
index 110556e..e3cfcd1 100644
--- a/rc_hip/repapp/views.py
+++ b/rc_hip/repapp/views.py
@@ -14,15 +14,15 @@ from django.contrib import messages
 from django.views import generic
 from django.urls import reverse_lazy
 from django.shortcuts import get_object_or_404, render
-from django.http import HttpResponseRedirect
+from django.http import HttpResponseRedirect, HttpResponse
 from django.core.exceptions import PermissionDenied
-from django.contrib import messages
 from django.contrib.auth.decorators import login_required
 from django.contrib.auth import authenticate, login
 from django.utils.timezone import now
-from repapp.models import CustomUser, Organisator, Reparateur
-from .models import Cafe, Device, Guest, OneTimeLogin
 from .forms import RegisterDevice, RegisterGuest
+from .models import (Cafe, Device, Guest, OneTimeLogin,
+                     CustomUser, Organisator, Reparateur)
+from . import mail_interface
 
 
 def send_one_time_login_mail(secret, mail, request):
@@ -216,11 +216,15 @@ class RegisterDeviceFormView(generic.edit.FormView):
         device.save()
 
         guest = Guest.objects.filter(mail=mail).first()
+        user = CustomUser.objects.filter(email=mail).first()
 
-        if guest:
+        if guest and user:
             device.guest = guest
             device.save()
 
+            guest.user = user
+            guest.save()
+
             send_confirmation_mails(device, guest, cafe, self.request)
 
             resp = HttpResponseRedirect(
@@ -407,14 +411,15 @@ def cron(request):
     """
     View to trigger automated regular tasks.
     """
-    pass
+    return HttpResponse('done.')
 
 
 def process_mails(request):
     """
     View to trigger processing of email in inbox.
     """
-    pass
+    count = mail_interface.process_mails()
+    return HttpResponse(f'Done. Processed {count} messages.')
 
 
 def one_time_login(request, secret: str):
diff --git a/requirements_dev.txt b/requirements_dev.txt
index 66f1b07..fce3d99 100644
--- a/requirements_dev.txt
+++ b/requirements_dev.txt
@@ -11,3 +11,4 @@ mozilla-django-oidc==3.0.0
 djlint==1.23.3
 django-import-export==3.2.0
 selenium==4.9.0
+imap-tools==1.0.0
diff --git a/requirements_prod.txt b/requirements_prod.txt
index 8013a0c..0eb9641 100644
--- a/requirements_prod.txt
+++ b/requirements_prod.txt
@@ -5,3 +5,4 @@ crispy-bootstrap4==2022.1
 crispy-bootstrap5==0.7
 mozilla-django-oidc==3.0.0
 django-import-export==3.2.0
+imap-tools==1.0.0