Fetchmail/Sendmail rejects

[Chuck Swiger]

Malcolm Kay wrote:
[ ... ]
> Thanks guys for the responses -- this really looks the way to go.
> 
> Does anyone know how sendmail distinguishes between:
>  reject=451 4.1.8 Domain of sender address ................ does not resolve
>  reject=553 5.1.8 .......... Domain of sender address .............. does not exist
> It seems the former is to be interpreted as a 'temporary' condition while the latter
> is to be interpreted as 'permanent' (and is by default deleted by fetchmail)?

Sendmail pays attention to the return value from doing DNS queries.  If 
sendmail receives an NXDOMAIN response, it treats that as a permanent, 5xx 
failure code.  If sendmail gets a timeout/TRY_AGAIN, it will return a 4xx temp 
failure.

It's not clear to me why this would matter if your ISP is the one running the 
mailserver: they aren't accepting the message in either case, which ought to 
mean that fetchmail will never see it.

-- 
-Chuck