Comments on: Messages Queuing with Error 451 4.4.0 DNS Query Failed

By: James Robbins

James Robbins — Wed, 20 May 2020 19:33:21 +0000

Worked for me! Thanks!
What a stupid bug… just check a box and restart a service. SBS 2011 Server.
Shouldn’t even have mattered. It IS the transport server already, and has worked for years.

By: aa@aa.lt

aa@aa.lt — Thu, 05 Sep 2019 05:09:45 +0000

This command mentioned above “dnscmd /config /enableednsprobes 0” and restarting transport service worked for me, but I hate this kind of stuff.

Why then other domains are successful? And why another Exchange (2013) using the same DNS server sends to specific domain (in my case is outlook.com) normally?

By: R Artes

R Artes — Tue, 02 Apr 2019 12:03:42 +0000

Thanks Paul, this worked for me too.

By: Luca

Luca — Fri, 26 Oct 2018 08:59:37 +0000

Thank you! That solved the issue for me too!

By: Scott

Scott — Wed, 18 Jul 2018 20:29:28 +0000

This post from almost four years old solved my problem.

By: Rae

Rae — Wed, 16 May 2018 01:32:29 +0000

Hi Paul,

Do you know how this error occur?
“451 4.4.397 Error communicating with target host. _> 421 4.4.2 Connection Dropped due to TimedOut”

Is this error came from the network side?

By: Daniel

Daniel — Mon, 11 Dec 2017 00:41:44 +0000

This is still helping people! Solve my issue on Server2008r2 and Ex2010. Thanks heaps! Saved my arse.

By: Gorazd Novsak

Gorazd Novsak — Wed, 25 Oct 2017 10:42:16 +0000

How can this still be an issue after all that time. And fix/workaround put out by MS is crazy… This is simple and I know it will work for all domains…

By: Kris

Kris — Sat, 12 Aug 2017 15:59:13 +0000

Thanks for this! We started to experience this when our DNS provider implemented DNS SEC on their end. In our case we did not have to restart any services for the queues to clear.

By: Eric

Eric — Sun, 30 Jul 2017 03:24:45 +0000

Thanks Paul! That was the solution I needed.