Does anyone know where I can get a list of the recommended error codes and their translations for bounced and returned mail messages. I am looking for ways to interpret the following type of codes... ----- Transcript of session follows ----- ... while talking to mail.crl.com.: >>> RCPT To:<[log in to unmask]> <<< 553 <[log in to unmask]>... we do not relay 550 <[log in to unmask]>... User unknown Something like a list of numbers followed by a better translation. Especially when I try to figure out the difference between a full mailbox and a server failure. Any help? TIA Paul Rice mailto:[log in to unmask]