This error message indicates that we've attempted to make a connection with your recipient's server but didn't receive a reply. Some possible causes include the following:
- The other domain doesn't have up-to-date MX records or is otherwise misconfigured.
- The other domain is blacklisting or graylisting messages from Gmail.
- The other domain is experiencing temporary networking problems.
We recommend contacting the customer service department of the recipient's domain for further instructions. If you receive this bounce message when sending to your Google Apps domain, please see our instructions for configuring your MX records.