> On 2016-11-02 11:36, Wietse Venema wrote: >> NOQUEUE: reject: RCPT from unknown[x.x.x.x]: 450 4.7.1 Client host >> rejected: cannot find your hostname, [x.x.x.x] > > Note that this is a 450 status, because the name server did not reply. > A proper SMTP client will therefore try to deliver the email later.
but looking in my logs, I see also 450 status when nameserver is reachable, but hostname could not be resolved (because it does not exist) In other words, from the logs I cannot tell the difference whether nameserver was offline, or IP simply does not resolve.
