diff --git a/django_mailbox/models.py b/django_mailbox/models.py
index 0ef088b..e7e9aef 100644
--- a/django_mailbox/models.py
+++ b/django_mailbox/models.py
@@ -387,7 +387,7 @@ class Mailbox(models.Model):
         msg.save()
         return msg
 
-    def get_new_mail(self):
+    def get_new_mail(self, condition=None):
         """Connect to this transport and fetch new messages."""
         new_mail = []
         connection = self.get_connection()
diff --git a/django_mailbox/tests/base.py b/django_mailbox/tests/base.py
index 3634c9a..621152f 100644
--- a/django_mailbox/tests/base.py
+++ b/django_mailbox/tests/base.py
@@ -55,12 +55,12 @@ class EmailMessageTestCase(TestCase):
         settings.EMAIL_USE_TLS = True
         super(EmailMessageTestCase, self).setUp()
 
-    def _get_new_messages(self, mailbox):
+    def _get_new_messages(self, mailbox, condition=None):
         maximum_wait = time.time() + self.maximum_wait_seconds
         while True:
             if time.time() > maximum_wait:
                 raise EmailIntegrationTimeout()
-            messages = self.mailbox.get_new_mail()
+            messages = self.mailbox.get_new_mail(condition)
             if messages:
                 return messages
             time.sleep(5)
diff --git a/django_mailbox/tests/test_integration_imap.py b/django_mailbox/tests/test_integration_imap.py
index 1dbee05..961cce9 100644
--- a/django_mailbox/tests/test_integration_imap.py
+++ b/django_mailbox/tests/test_integration_imap.py
@@ -24,12 +24,6 @@ class TestImap(EmailMessageTestCase):
             uri=self.get_connection_string()
         )
         self.arbitrary_identifier = str(uuid.uuid4())
-        settings.DJANGO_MAILBOX_INTEGRATION_TESTING_SUBJECT = (
-            self.arbitrary_identifier
-        )
-
-    def tearDown(self):
-        settings.DJANGO_MAILBOX_INTEGRATION_TESTING_SUBJECT = None
 
     def get_connection_string(self):
         return "imap+ssl://{account}:{password}@{server}".format(
@@ -50,7 +44,10 @@ class TestImap(EmailMessageTestCase):
         )
         msg.send()
 
-        messages = self._get_new_messages(self.mailbox)
+        messages = self._get_new_messages(
+            self.mailbox,
+            condition=lambda m: m['subject'] == self.arbitrary_identifier
+        )
 
         self.assertEqual(1, len(messages))
         self.assertEqual(messages[0].subject, self.arbitrary_identifier)
diff --git a/django_mailbox/transports/generic.py b/django_mailbox/transports/generic.py
index cf4bd78..2e1f979 100644
--- a/django_mailbox/transports/generic.py
+++ b/django_mailbox/transports/generic.py
@@ -16,10 +16,12 @@ class GenericFileMailbox(EmailTransport):
     def get_instance(self):
         return self._variant(self._path)
 
-    def get_message(self):
+    def get_message(self, condition=None):
         repository = self.get_instance()
         repository.lock()
         for key, message in repository.items():
+            if condition and not condition(message):
+                continue
             repository.remove(key)
             yield message
         repository.unlock()
diff --git a/django_mailbox/transports/imap.py b/django_mailbox/transports/imap.py
index 2ca39b2..cef3eb4 100644
--- a/django_mailbox/transports/imap.py
+++ b/django_mailbox/transports/imap.py
@@ -82,7 +82,7 @@ class ImapTransport(EmailTransport):
                 pass
         return safe_message_ids
 
-    def get_message(self):
+    def get_message(self, condition=None):
         message_ids = self._get_all_message_ids()
 
         if not message_ids:
@@ -105,10 +105,7 @@ class ImapTransport(EmailTransport):
                     continue
                 message = self.get_email_from_bytes(msg_contents[0][1])
 
-                if (
-                    self.integration_testing_subject and
-                    message['Subject'] != self.integration_testing_subject
-                ):
+                if condition and not condition(message):
                     continue
 
                 yield message
diff --git a/django_mailbox/transports/pop3.py b/django_mailbox/transports/pop3.py
index 8520557..4601114 100644
--- a/django_mailbox/transports/pop3.py
+++ b/django_mailbox/transports/pop3.py
@@ -28,7 +28,7 @@ class Pop3Transport(EmailTransport):
             return six.binary_type('\r\n', 'ascii').join(message_lines)
         return '\r\n'.join(message_lines)
 
-    def get_message(self):
+    def get_message(self, condition=None):
         message_count = len(self.server.list()[1])
         for i in range(message_count):
             try:
@@ -36,6 +36,10 @@ class Pop3Transport(EmailTransport):
                     self.server.retr(i + 1)[1]
                 )
                 message = self.get_email_from_bytes(msg_contents)
+
+                if condition and not condition(message):
+                    continue
+
                 yield message
             except MessageParseError:
                 continue