Report SMTP error with more info

hedgedoc-expire.py

@@ -60,11 +60,18 @@ class EmailSender:
         :param message: to be sent
         :return:
         """
+        try:
             smtp_server = smtplib.SMTP(self.hostname, port=self.port)
             context = ssl.create_default_context()
             smtp_server.starttls(context=context)
             smtp_server.login(self.username, self.password)
             smtp_server.send_message(message)
+        except Exception as e:
+            print(f'Unable to send mail through {self}: {e}')
+            raise e
+
+    def __str__(self):
+        return f'EmailSender<{self.hostname},{self.port},{self.username},{self.mail_from}>'
 
 
 class HedgedocExpire: