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451 4.4.0 DNS query failed. The error was: SMTPSEND.DNS.NonExistentDomain; nonexistent domain

This blog post is to address a specific issue with mailflow and DNS query

2 exchange 2010 servers – exch1 and exch2

Exch1 is the primary Exchange 2010 server and exch2 is the DR server.

Exch2 connects to the corporate network through VPN. (Don’t ask me why)

When exch2 is offline, mails starts queuing up in exch1 with the error:

451 4.4.0 DNS query failed. The error was: SMTPSEND.DNS.NonExistentDomain; nonexistent domain

This basically means that exch1 is trying to contact exch2 (for some reason) and failed to do so and the emails will be queued.

Did an nslookup to exch2 on exch1 and saw it cannot resolve the host. Checked in DNSMgmt.msc and saw the entry for exch2 is missing because the server connects through VPN.

If we create a dns A record, it will break functionality when exch1 is offline.

To resolve this, simply created a host record in exch1 for the ip for exch2, flushDNS, restart Trasport and mailflow resumed.

Reason for this could be multiple but I fixed all of them anyways…

  • Connect to ADSIEdit and ensure the attribute msExchRoutingMasterDN is set to Exch1.
  • Create a receive connector on Exch1 to accept emails from the mail gateway service (if any) and exch2
  • Check an ensure all Arbitration mailboxes are on Exch1 (was on exch2 in this case)


 


Some troubleshooting that can be useful:

First we need to determine the default route used by an email message when exch2 is online.

Perform MessageTracking as shown:

Subject: Subject is Blue Bear

Conclusion from Message tracking logs:

  • Hop 1 – Email reached exch1 from 10.1.1.141 (mail gateway) and delivered to exch1 (10.1.1.139)
  • Hop 2 – Email was routed from exch1 (HubMailboxCoexistence) with event HARedirect
  • Hop 3 – Exch1 used the “Intra-Organization SMTP Send Connector” and delivered the email to exch2
  • Hop 4 – Exch2 submitted the email to the mailbox using StoreDriver

[PS] C:\Windows\system32>Get-MessageTrackingLog -MessageSubject “Subject is Blue Bear” | Fl

RunspaceId : aadca1bc-dacf-4193-bceb-70d4f3042dad

Timestamp : 11/23/2013 2:38:21 AM

ClientIp : 10.1.1.141

ClientHostname : exchange-pop3-connector.com

ServerIp : 10.1.1.139

ServerHostname : exch1

SourceContext : 08D0B6064ED3A8F2;2013-11-23T07:38:19.623Z;0

ConnectorId : exch1\Internet

Source : SMTP

EventId : RECEIVE

InternalMessageId : 76273

MessageId : <00a101cee81e$b2024840$1606d8c0$@testing.com>

Recipients : {info@exchguru.com}

RecipientStatus : {}

TotalBytes : 36966

RecipientCount : 1

RelatedRecipientAddress :

Reference :

MessageSubject : Subject is Blue Bear

Sender : willy@testing.com

ReturnPath : willy@testing.com

MessageInfo : 10I: NTS:

MessageLatency :

MessageLatencyType : None

EventData : {[FirstForestHop, exch1.exchguru.local]}

 

RunspaceId : aadca1bc-dacf-4193-bceb-70d4f3042dad

Timestamp : 11/23/2013 2:38:21 AM

ClientIp :

ClientHostname :

ServerIp :

ServerHostname : exch1

SourceContext : HubMailboxCoexistence

ConnectorId :

Source : ROUTING

EventId : HAREDIRECT

InternalMessageId : 76273

MessageId : <00a101cee81e$b2024840$1606d8c0$@testing.com>

Recipients : {info@exchguru.com}

RecipientStatus : {}

TotalBytes : 36966

RecipientCount : 1

RelatedRecipientAddress :

Reference :

MessageSubject : Subject is Blue Bear

Sender : willy@testing.com

ReturnPath : willy@testing.com

MessageInfo :

MessageLatency :

MessageLatencyType : None

EventData :

 

RunspaceId : aadca1bc-dacf-4193-bceb-70d4f3042dad

Timestamp : 11/23/2013 2:38:23 AM

ClientIp : 10.1.1.139

ClientHostname : exch1

ServerIp : 10.1.1.137

ServerHostname : exch2.exchguru.local

SourceContext : 08D0B6064ED3A8F3;250 2.6.0 <00a101cee81e$b2024840$1606d8c0$@testing.com> [InternalId=17] Queued mail for delivery

ConnectorId : Intra-Organization SMTP Send Connector

Source : SMTP

EventId : SEND

InternalMessageId : 76273

MessageId : <00a101cee81e$b2024840$1606d8c0$@testing.com>

Recipients : {info@exchguru.com}

RecipientStatus : {250 2.1.5 Recipient OK}

TotalBytes : 37375

RecipientCount : 1

RelatedRecipientAddress :

Reference :

MessageSubject : Subject is Blue Bear

Sender : willy@testing.com

ReturnPath : willy@testing.com

MessageInfo : 2013-11-23T07:38:20.481Z;LSRV=exch1.exchguru.local:TOTAL=3|SMR=1|SMS=1

MessageLatency : 00:00:03.1040000

MessageLatencyType : LocalServer

EventData :

 

RunspaceId : aadca1bc-dacf-4193-bceb-70d4f3042dad

Timestamp : 11/22/2013 7:21:05 AM

ClientIp : fe80::4403:3bf6:2b52:fe4a%15

ClientHostname : exch1

ServerIp :

ServerHostname : exch2

SourceContext : MDB:029914e8-5057-4db9-8833-56d916deaee6, Mailbox:2baf5b54-fc60-4b31-b77e-b411cb6ac837, Event

:5215992, MessageClass:IPM.Note, CreationTime:2013-11-22T12:21:01.826Z, ClientType:MOMT

ConnectorId :

Source : STOREDRIVER

EventId : SUBMIT

InternalMessageId :

MessageId : <117C42489568724A88B1041BA91964742FDE79DE@exch1.exchguru.local>

Recipients : {}

RecipientStatus : {}

TotalBytes :

RecipientCount :

RelatedRecipientAddress :

Reference :

MessageSubject : Subject is Blue Bear

Sender : info@exchguru.com

ReturnPath :

MessageInfo : 2013-11-22T12:21:01.826Z;LSRV=exch1.exchguru.local:TOTAL=3

MessageLatency : 00:00:03.9940000

MessageLatencyType : LocalServer

EventData : {[ItemEntryId, 00-00-00-00-4D-07-DA-8A-24-6B-D1-42-B6-5E-26-2E-EA-91-73-82-07-00-11-7C-42-48-

95-68-72-4A-88-B1-04-1B-A9-19-64-74-00-00-00-86-BC-5C-00-00-11-7C-42-48-95-68-72-4A-88-B1-04-

1B-A9-19-64-74-00-00-2F-D9-6B-AB-00-00]}

[PS] C:\Windows\system32>

Use this cmdlet to view the queue and error:

[PS] C:\Windows\system32>Get-Queue | fl

RunspaceId : aadca1bc-dacf-4193-bceb-70d4f3042dad

DeliveryType : SmtpRelayWithinAdSite

NextHopDomain : hub version 14

TlsDomain :

NextHopConnector : 61027a30-e9a9-4c2d-acb5-c1efc96d5d8b

Status : Retry

MessageCount : 4

LastError : 451 4.4.0 DNS query failed. The error was: SMTPSEND.DNS.NonExistentDomain; nonexistent domain

LastRetryTime : 11/22/2013 7:04:53 PM

NextRetryTime : 11/22/2013 7:05:53 PM

DeferredMessageCount : 0

QueueIdentity : exch1\26716

Identity : exch1\26716

IsValid : True

RunspaceId : aadca1bc-dacf-4193-bceb-70d4f3042dad

DeliveryType : SmtpRelayWithinAdSite

NextHopDomain : hub version 14

TlsDomain :

NextHopConnector : 61027a30-e9a9-4c2d-acb5-c1efc96d5d8b

Status : Ready

MessageCount : 0

LastError : 451 4.4.0 Primary target IP address responded with: “421 4.2.1 Unable to connect.” Attempted failover to alternate host, but that did not succeed. Either there are no alternate hosts, or delivery failed to all alternate hosts.Queue will be resubmitted for routing for MAPI delivery

LastRetryTime : 11/22/2013 7:59:25 PM

Ratish Nair

Microsoft MVP | Exchange Server

Team @MSExchangeGuru

2 Responses to “451 4.4.0 DNS query failed. The error was: SMTPSEND.DNS.NonExistentDomain; nonexistent domain”

  1. NeWay Technologies – Weekly Newsletter #71 – November 28, 2013 | NeWay Says:

    […] 451 4.4.0 DNS query failed. The error was: SMTPSEND.DNS.NonExistentDomain; nonexistent domain – […]

  2. NeWay Technologies – Weekly Newsletter #71 – November 29, 2013 | NeWay Says:

    […] 451 4.4.0 DNS query failed. The error was: SMTPSEND.DNS.NonExistentDomain; nonexistent domain – […]

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