Since demoting a child domain a few days ago, Exchange 2013 is still trying to contact it and as a result generating errors in the application event logs.  I had a similar problem which I solved by removing some old migration batches, now I have a problem with the Microsoft Exchange Mailbox Replication service.

The event logged is:

The Microsoft Exchange Mailbox Replication service was unable to process a request due to an unexpected error.
Request GUID: '0b6c0f5a-0563-48e2-8b97-e0781c6cc69a' 
Database GUID: '23258311-ad29-41c2-a842-522f48baa267'
Error: Unable to read from Active Directory. --> The call to Microsoft Exchange Active Directory Topology service on server 'TopologyClientTcpEndpoint (localhost)' returned an error. Error details Unable to find a suitable directory server for domain 'admin.riddlesdown.local'.. --> Unable to find a suitable directory server for domain 'admin.riddlesdown.local'..

Process Microsoft.Exchange.Directory.TopologyService.exe (PID=2280). Exchange Active Directory Provider could not find an available domain controller in domain admin.riddlesdown.local. This event may be caused by network connectivity issues or configured incorrectly DNS server.

The domain doesn't exist in AD Sites and Services, I have removed all traces from DNS but this is still occurring.  When I run Get-ADServerSettings | fl it reports no trace of the domain or a DC that was previously in it.

How can I stop these events occurring and is it likely to be causing something else not to work correctly.

We are running Exchange 2013 CU1

Hello,

Please make sure whether there are other DCs . If there are other DCs, I recommend you use set-adserversettings cmdlet to specify a DC for your exchange server.

Set-AdServerSettings

http://technet.microsoft.com/en-us/library/dd298063(v=exchg.150).aspx

If the issue persists, please post the event source and event id.

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No, that didn't work.  Here are more details:

Source: MSExchange ADAccess (EventID: 2130)

Process Microsoft.Exchange.Directory.TopologyService.exe (PID=2280). Exchange Active Directory Provider could not find an available domain controller in domain admin.riddlesdown.local. This event may be caused by network connectivity issues or configured incorrectly DNS server.

Source: MSExchange ADAccess (EventID: 2119)

Process Microsoft.Exchange.Directory.TopologyService.exe (PID=2280). Error DNS_ERROR_RCODE_NAME_ERROR (0x8007232B) occurred when DNS was queried for the service location (SRV) resource record used to locate a domain controller for domain admin.riddlesdown.local
 The query was for the SRV record for _ldap._tcp.dc._msdcs.admin.riddlesdown.local
 Common causes of this error include the following:
 - The DNS SRV records required to locate a domain controller for the domain are not registered in DNS. These records are registered with a DNS server automatically when a domain controller is added to a domain. They are updated by the domain controller at set intervals. This computer is configured to use DNS servers with following IP addresses:
10.59.100.7
10.59.100.8
fec0:0:0:ffff::1Microsoft.Exchange.Directory.TopologyService.exe
fec0:0:0:ffff::2Microsoft.Exchange.Directory.TopologyService.exe
fec0:0:0:ffff::3Microsoft.Exchange.Directory.TopologyService.exe

 - One or more of the following zones do not include delegation to its child zone:
admin.riddlesdown.local
riddlesdown.local
local
. (the root zone)

Source: MSExchange Mailbox Replication Service (EventID: 1121)

The Microsoft Exchange Mailbox Replication service was unable to process a request due to an unexpected error.
Request GUID: '87f4b926-0621-43d3-afeb-fe475ee6d850' 
Database GUID: '23258311-ad29-41c2-a842-522f48baa267'
Error: Unable to read from Active Directory. --> The call to Microsoft Exchange Active Directory Topology service on server 'TopologyClientTcpEndpoint (localhost)' returned an error. Error details Unable to find a suitable directory server for domain 'admin.riddlesdown.local'.. --> Unable to find a suitable directory server for domain 'admin.riddlesdown.local'..

Something is cause the Exchange server to go looking for our old domain, but what and why?

Hello,

From the error, your exchange is looking for old domain.

Please make sure whether your exchange server is installed in the old domain . If so, there may be not change the domain, but you can change the DCs for the domain.

If there are other Dcs in the domain, you can use the cmdlet as I provide.

Besides, I recommend you use server health and performance to check if there is any error for your exchange server.

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