Exchange 2013: 451 4.7.0 Temporary Server errors. Please Try Again Later. PRX

Problem: Exchange 2013 Mail Stuck and can't get delivered to other Exchange 2013 or WAN.

Error you see: 451 4.7.0 Temporary Server error. Please Try Again Later. PRX

This is related to some DNS resolution bug. Solving it may include "Old days" HOSTS File ;-)

1. Check name resolution with nslookup
2. Check the your Exchange Server has two correct DNS on the NIC-card of the OS (One does not solve it) Use external if you don't have two DC
3. Change the Default frontend Connector to use fixed DNS
4. Change the Exchange Server itself to user fixed DNS
5. Add the exchange to the c:\windows\system32\drivers\etc\hosts File as Short and FQDN (See below)

Start ECP

Message Flow

Change the Default Frontend YOURSERVERNAME (With the pencil)

Down below change "All unassigned" to your Exchange 2013 Server IPV4 address"

Change the DNS that Exchange USES (Make it hard coded).

ABOVE the one or two Internal DNS and maybe 8.8.8.8 or your providers Uplink DNS

Below your one or two internal DNS

This MAY sound confusing but sometimes there is no other way:

Adapt the HOSTS file:

Do this is CMD so you find it ;-)

Add or Change the HOSTS file to:

192.168.X.X Yourexchange2013            [ sample : 192.168.1.20 exc2013-16cas) ]

192.168.X.X YourexchangeFQDNname        [ sample: 192.168.1.20 exc2013-16cas.butsch.ch) ]