diff --git a/colab/super_archives/management/commands/message.py b/colab/super_archives/management/commands/message.py
index 1ce06f9..bf86c73 100644
--- a/colab/super_archives/management/commands/message.py
+++ b/colab/super_archives/management/commands/message.py
@@ -79,7 +79,7 @@ class Message(mailbox.mboxMessage):
             return body.strip()
 
     def get_received_datetime(self):
-        if self not in ('Received'):
+        if ('Received') not in self:
             return None
         # The time received should always be the last element
         #   in the `Received` attribute from the message headers
--
libgit2 0.21.2