diff --git a/README.md b/README.md
index 95a065c..cd11125 100644
--- a/README.md
+++ b/README.md
@@ -2,7 +2,7 @@
 
 purpose: gather data from intern(WMDE) and extern(volunteers) forms to create a database ('förderdatenbank') and send emails with links for a questionary.
 
-used versions:
+versions used in development:
 
 python 3.8.2
 django 3.1.1
diff --git a/input/forms.py b/input/forms.py
index c7d71e3..b348afd 100644
--- a/input/forms.py
+++ b/input/forms.py
@@ -13,7 +13,7 @@ class ProjectForm(ModelForm):
 
     class Meta:
         model = Project
-        exclude = ('pid', 'granted', 'username', 'realname', 'email')
+        exclude = ('pid', 'granted', 'username', 'realname', 'email', 'project_end_mail')
         widgets = {'start': AdminDateWidget(),
                    'end': AdminDateWidget(),}
 
diff --git a/input/management/commands/sendmails.py b/input/management/commands/sendmails.py
index 35112ce..6d4c4fd 100644
--- a/input/management/commands/sendmails.py
+++ b/input/management/commands/sendmails.py
@@ -26,7 +26,10 @@ class Command(BaseCommand):
     def handle(self, *args, **options):
 
         # get all projects which ended 3 weeks ago
-        old = Project.objects.filter(end__lt = date.today() - timedelta(days=30))
+        old = Project.objects.filter(end__lt = date.today() - timedelta(days=21))\
+                             .exclude(end_mail_send = True)
+
+
         print(old)
         mail_template = get_template('input/if_end_of_project.txt')
         for project in old:
@@ -39,6 +42,8 @@ class Command(BaseCommand):
                           IF_EMAIL,
                           [IF_EMAIL],
                           fail_silently=False)
+                project.end_mail_send = True
+                project.save()
             except BadHeaderError:
                 return HttpResponse('Invalid header found.')
 
diff --git a/input/migrations/0020_project_project_end_mail.py b/input/migrations/0020_project_project_end_mail.py
new file mode 100644
index 0000000..465e443
--- /dev/null
+++ b/input/migrations/0020_project_project_end_mail.py
@@ -0,0 +1,18 @@
+# Generated by Django 3.1.1 on 2020-10-22 09:07
+
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('input', '0019_auto_20201021_1148'),
+    ]
+
+    operations = [
+        migrations.AddField(
+            model_name='project',
+            name='project_end_mail',
+            field=models.BooleanField(null=True),
+        ),
+    ]
diff --git a/input/migrations/0021_auto_20201022_0934.py b/input/migrations/0021_auto_20201022_0934.py
new file mode 100644
index 0000000..e9f3f61
--- /dev/null
+++ b/input/migrations/0021_auto_20201022_0934.py
@@ -0,0 +1,18 @@
+# Generated by Django 3.1.1 on 2020-10-22 09:34
+
+from django.db import migrations
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('input', '0020_project_project_end_mail'),
+    ]
+
+    operations = [
+        migrations.RenameField(
+            model_name='project',
+            old_name='project_end_mail',
+            new_name='end_mail_send',
+        ),
+    ]
diff --git a/input/models.py b/input/models.py
index dfa3145..fb169b6 100644
--- a/input/models.py
+++ b/input/models.py
@@ -2,6 +2,7 @@ from django.db import models
 
 from .settings import ACCOUNTS
 
+
 class Volunteer(models.Model):
     realname = models.CharField(max_length=200, null=True)
     email = models.CharField(max_length=200, null=True)
@@ -17,6 +18,7 @@ class Volunteer(models.Model):
     class Meta:
         abstract = True
 
+
 class Project(Volunteer):
     name = models.CharField(max_length=200)
     start = models.DateField('Startdatum', null=True)
@@ -24,7 +26,9 @@ class Project(Volunteer):
     account = models.CharField('Kostenstelle', max_length=5,
                                 choices=ACCOUNTS.items(), null=True,)
 
-    pid = models.IntegerField(null=True, blank=True) # automaticly generated
+    # the following Fields are not supposed to be editet by users
+    pid = models.IntegerField(null=True, blank=True)
+    end_mail_send = models.BooleanField(null=True)
 
     def save(self,*args,**kwargs):
         # is there a way to call super().save() only once?
@@ -35,6 +39,7 @@ class Project(Volunteer):
     def __str__(self):
         return f"{self.pid} {self.name}"
 
+
 class HonoraryCertificate(Volunteer):
     request_url = models.CharField(max_length=2000)
     project = models.ForeignKey(Project, null = True, on_delete = models.SET_NULL)
@@ -42,7 +47,8 @@ class HonoraryCertificate(Volunteer):
     def __str__(self):
         return "Certificate for " + self.realname
 
-#abstract class for Library, IFG, ...
+
+#abstract base class for Library, IFG, ...
 class Grant(Volunteer):
     cost = models.CharField(max_length=10)
     notes = models.CharField(max_length=500)
@@ -60,6 +66,7 @@ TYPE_CHOICES = {'BIB': 'Bibliotheksstipendium',
            'IFG': 'Kostenübernahme IFG-Anfrage',
            'LIT': 'Literaturstipendium',}
 
+
 # same model is used for Library, ELitStip and Software!
 class Library(Grant):
 
@@ -74,6 +81,7 @@ class Library(Grant):
     def __str__(self):
         return self.library
 
+
 class IFG(Grant):
     url = models.CharField(max_length=2000)