One regular correspondent reports that his messages are being rejected on occasion. The message he gets back says, "This is the mail system at host smtprelay03.b.hostedemail.com. I'm sorry to have to inform you that your message could not be delivered to one or more recipients. It's attached below. For further assistance, please send mail to postmaster. If you do so, please include this problem report. You can delete your own text from the attached returned message.” This is apparently an issue with an intermediary relayer of messages. How can we fix the problem?