On Mon, Sep 16, 2019 at 01:44:38PM +0200, Helmut Schneider wrote:
> Sep 16 06:08:09 h2786452 postfix-in/smtp[12937]: 194853E04AA: to=<info@>,
> relay=none, delay=0.01, delays=0.01/0/0.01/0, dsn=5.4.4, status=bounced
> (Host or domain name not found. Name service error for name=exchange01
> type=AAAA: Host not found)
You should explain how the name "exchange01" becomes the nexthop
destination for mail to "<info@>" (which does not look like a
valid email address).
> I already created an entry in the hosts file without success.
By default, the Postfix smtp(8) delivery agent does not consult
/etc/hosts:
http://www.postfix.org/postconf.5.html#smtp_host_lookup
> Where can I change the DSN to 4xx and ensure that mails are delivered when
> the tunnel is up again?
Normally, if a tunnel goes down, DNS lookups that require access
to a server on the far side of the tunnel tempfail, and Postfix
would automatically return 4XX. If your system returns hard errors
when the network is partly down, then that's a configuration defect
with the system.
--
Viktor.
