According to Magnus Bodin:
>
> On Tue, May 23, 2000 at 07:59:24PM +0100, Chris Green wrote:
> >
> > Secondly what does that (#4.4.1) mean? I can't find any paragraph
> > number 4.4.1 in the documentation.
>
>
> It's defined in RFC 1839 <http://rfc1839.x42.com/>
Small typo above, it's actually, RFC1893 <http://rfc1893.x42.com/>
> 4.X.X Persistent Transient Failure
> A persistent transient failure is one in which the message as
> sent is valid, but some temporary event prevents the successful
> sending of the message. Sending in the future may be successful.
>
> X.4.X Network and Routing Status
> The networking or routing codes report status about the
> delivery system itself. These system components include any
> necessary infrastructure such as directory and routing
> services. Network issues are assumed to be under the
> control of the destination or intermediate system
> administrator.
>
> X.4.1 No answer from host
> The outbound connection attempt was not answered, either
> because the remote system was busy, or otherwise unable to
> take a call. This is useful only as a persistent transient
> error.
--curtis
