diff --git a/mayan/apps/sources/models.py b/mayan/apps/sources/models.py
index 9b204388d2..dc9d0c3f39 100644
--- a/mayan/apps/sources/models.py
+++ b/mayan/apps/sources/models.py
@@ -1,9 +1,13 @@
 from __future__ import absolute_import
 
 from ast import literal_eval
+from email.Utils import collapse_rfc2231_value
+from email import message_from_string
 import json
+import imaplib
 import logging
 import os
+import poplib
 
 from django.contrib.contenttypes import generic
 from django.contrib.contenttypes.models import ContentType
@@ -26,8 +30,8 @@ from .literals import (DEFAULT_INTERVAL, DEFAULT_POP3_TIMEOUT,
                        SOURCE_CHOICES_PLURAL, SOURCE_CHOICE_STAGING,
                        SOURCE_CHOICE_WATCH, SOURCE_CHOICE_WEB_FORM,
                        SOURCE_INTERACTIVE_UNCOMPRESS_CHOICES,
-                       SOURCE_UNCOMPRESS_CHOICES, SOURCE_CHOICE_EMAIL_IMAP,
-                       SOURCE_CHOICE_EMAIL_POP3)
+                       SOURCE_UNCOMPRESS_CHOICES, SOURCE_UNCOMPRESS_CHOICE_Y,
+                       SOURCE_CHOICE_EMAIL_IMAP, SOURCE_CHOICE_EMAIL_POP3)
 from .managers import SourceTransformationManager
 
 logger = logging.getLogger(__name__)
@@ -36,6 +40,7 @@ logger = logging.getLogger(__name__)
 class Source(models.Model):
     title = models.CharField(max_length=64, verbose_name=_(u'Title'))
     enabled = models.BooleanField(default=True, verbose_name=_(u'Enabled'))
+    # TODO: remove whitelist and blacklists
     whitelist = models.TextField(blank=True, verbose_name=_(u'Whitelist'), editable=False)
     blacklist = models.TextField(blank=True, verbose_name=_(u'Blacklist'), editable=False)
 
@@ -199,32 +204,41 @@ class IntervalBaseModel(OutOfProcessSource):
     document_type = models.ForeignKey(DocumentType, null=True, blank=True, verbose_name=_('Document type'), help_text=_('Assign a document type to documents uploaded from this source.'))
     uncompress = models.CharField(max_length=1, choices=SOURCE_UNCOMPRESS_CHOICES, verbose_name=_('Uncompress'), help_text=_('Whether to expand or not, compressed archives.'))
 
+    def _get_periodic_task_name(self, pk=None):
+        return 'check_interval_source-%i' % (pk or self.pk)
+
+    def _delete_periodic_task(self, pk=None):
+        periodic_task = PeriodicTask.objects.get(name=self._get_periodic_task_name(pk))
+
+        interval_instance = periodic_task.interval
+
+        if tuple(interval_instance.periodictask_set.values_list('id', flat=True)) == (periodic_task.pk,):
+            # Only delete the interval if nobody else is using it
+            interval_instance.delete()
+        else:
+            periodic_task.delete()
+
     def save(self, *args, **kwargs):
         new_source = not self.pk
         super(IntervalBaseModel, self).save(*args, **kwargs)
-        periodic_task_name = 'check_interval_source-%i' % self.pk
-        if new_source:
-            interval_instance = IntervalSchedule.objects.create(every=self.interval, period='seconds')
-            PeriodicTask.objects.create(
-                name=periodic_task_name,
-                interval=interval_instance,
-                task='sources.tasks.task_check_interval_source',
-                queue='mailing',
-                kwargs=json.dumps({'source_id': self.pk})
-            )
-        else:
-            periodic_task = PeriodicTask.objects.get(name=periodic_task_name)
-            periodic_task.interval.every = self.interval
-            periodic_task.interval.save()
-            periodic_task.save()
+
+        if not new_source:
+            self._delete_periodic_task()
+
+        interval_instance, created = IntervalSchedule.objects.get_or_create(every=self.interval, period='seconds')
+        # Create a new interval or reuse someone else's
+        PeriodicTask.objects.create(
+            name=self._get_periodic_task_name(),
+            interval=interval_instance,
+            task='sources.tasks.task_check_interval_source',
+            queue='mailing',
+            kwargs=json.dumps({'source_id': self.pk})
+        )
 
     def delete(self, *args, **kwargs):
-        periodic_task_name = 'check_interval_source-%i' % self.pk
+        pk = self.pk
         super(IntervalBaseModel, self).delete(*args, **kwargs)
-        periodic_task = PeriodicTask.objects.get(name=periodic_task_name)
-        interval_instance = periodic_task.interval
-        periodic_task.delete()
-        interval_instance.delete()
+        self._delete_periodic_task(pk)
 
     class Meta:
         verbose_name = _('Interval source')
@@ -239,6 +253,7 @@ class EmailBaseModel(IntervalBaseModel):
     password = models.CharField(max_length=96, verbose_name=_('Password'))
 
     # From: http://bookmarks.honewatson.com/2009/08/11/python-gmail-imaplib-search-subject-get-attachments/
+    # TODO: Add lock to avoid being running more than once concurrent
     @staticmethod
     def process_message(source, message):
         email = message_from_string(message)
@@ -347,7 +362,7 @@ class IMAPEmail(EmailBaseModel):
             mailbox.close()
             mailbox.logout()
         except Exception as exception:
-            logger.error('Unhandled exception: %s' % exc)
+            logger.error('Unhandled exception: %s' % exception)
             # TODO: Add user notification
 
     class Meta: