On Tue, 12 Sep 2000 12:03:54 +1100, Michael Shannon <[log in to unmask]>
wrote:

>Does anyone know if there is some sort of a list available for mail delivery
>error codes?  I know that there's no definitive stadard (yet) but surely
>most mail servers use similar codes.  I just find it difficult to sort out
>what an error might be caused by when all I have is a code without an
>explanation.

See RFC 821 (The original SMTP specification) and RFC 1893 (Delivery Status
Notification system)  One source for these RFCs is 

 http://www.imc.org/mail-standards.html

but there are several other places as well.