To enable us to investigate errors or problems you should provide us
with the following information (or as much of it as possible):

 * the IP, 
 * the Time (including timezone), 
 * the Message-Id, 
 * the Adresses you sent from and to, 
 * maybe some more things that could be related with that problem.

We maintain a system with more than 150,000 subscribers which receives
and sends more than 1,000,000 mails a day. Without the information
above we have little chance of finding out what went wrong.