29 comments on “451 4.7.0 Temporary server error. Please try again later. PRX2

  1. Thanks – spot on on my problem! I had network adapter configured with one internal DNS and one external. Remove external DNS server and ipconfig /flushdns and emails was flying in and out.
    I guess Exchange 2013 is a little more sensitive to DNS as opposed to Exchange 2010. The external domainname for emails exists in internal DNS so strange that the exchange 2013 will goΒ΄to external DNS to lookup names…
    Thanks again πŸ™‚

    BR Soren

  2. Finally a solution that solve my very same issue. Spend hours trying to undo/redo the settings in EAC without much help. Glad I came across this fix

  3. Thanks i was stumped on this one for a while I was sending internal external and receiving internal but not receiving external emails i tried this link to troubleshoot https://testconnectivity.microsoft.com which i then found the error which led me to this page. You wouldn’t think something so simple that works on older servers would be the issue. Great find!!

  4. Holy crap!! .. days … more configuration changes than Carter has little liver pills. The pile of hair I’ve pulled out has reached my seat.

    Thank you.

  5. Like a charm! Lab is now up and sending mail both ways successfully! Thanks for that tidbit. After changing both the Internal DNS Lookups and External DNS Lookups to use the specified DNS server, I would have figured that I was good to go, but nope. I had to actually remove the DNS Server entries from the NIC that I didn’t want to use. Crazy. Given that I spend most of my time on Lync and Skype for Business servers, this posting really prevented me from chasing my tail in circles with Exchange. Thanks so much!

  6. I recently ran into the same issue. I tried the suggestions here and made some progress, but I still couldn’t get past the send test message step. I noticed that when I turned off the IPV6 on my NICs, that my MX lookups stopped resolving to my server (I’m using WIX)…SO i had to turn it back on. This lead me to think that even though I only had the internal DNS server’s IP listed, that this only applied to the IP4 settings. The IPV6 settings were using a DHCP DNS setting, which I pinged and found out that it was Comcast. So I went into the NIC and put my IPV6 address as the IPV6 DNS and voila!! Just thought I’d share this and hope it makes sense (i’m a beginner at Exchange).

  7. Thanks so much. Home test system, and I too, had put the router in as the second DNS entry. I guess how it works is that you only need that entry on your DNS server, so that it will go to the router to get external sites.

  8. What can I say installed a new server, set the second DNS to point externally, thinking it was a good thing – soon as I deleted bang about 30 emails – your a star thank you

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