Hello,

Can someone please advise...

There were no changes that I was aware of in my lab but I now have no mail flow. When testing with Exchange Connectivity Tester I get:

 The server returned status code 451 - Error in processing. The server response was: 4.7.0 Temporary server error. Please try again later. PRX5
Exception details:
Message: Error in processing. The server response was: 4.7.0 Temporary server error. Please try again later. PRX5
Type: System.Net.Mail.SmtpException
Stack trace:
at System.Net.Mail.DataStopCommand.CheckResponse(SmtpStatusCode statusCode, String serverResponse)
at System.Net.Mail.DataStopCommand.Send(SmtpConnection conn)
at System.Net.Mail.SmtpClient.Send(MailMessage message)
at Microsoft.Exchange.Tools.ExRca.Tests.SmtpMessageTest.PerformTestReally()
Elapsed Time: 24526 ms. 

I am running a single Exchange 2013 Server on a VM!

There seem to be plenty of resources to run it and autodiscovery works, Outlook connects but no mail flows and external mail bounces!

Can anyone advise where I am going wrong?

This is most likely a DNS issue.

You should try updating your transport services (frontend and otherwise.) You can see what they're set currently in the management shell with these;

Get-FrontendTransportService 
Get-TransportService

Check out the ExternalDNS settings and get them set to whatever your DNS should be (with Set- rather than Get- behind each command) and make sure your Exchange server is a part of those DNS records too!

Hello,

Many thanks for that, I had a look and there seem to be a few things wrong...

[PS] C:\Windows\system32>Get-TransportService | fl *DNS*

ExternalDNSAdapterEnabled : True
ExternalDNSAdapterGuid    : d112e046-de54-4bcb-b50b-2f645d5fbe97
ExternalDNSProtocolOption : Any
ExternalDNSServers        : {8.8.4.4, 8.8.8.8}
InternalDNSAdapterEnabled : True
InternalDNSAdapterGuid    : d112e046-de54-4bcb-b50b-2f645d5fbe97
InternalDNSProtocolOption : Any
InternalDNSServers        : {}
DnsLogMaxAge              : 7.00:00:00
DnsLogMaxDirectorySize    : 100 MB (104,857,600 bytes)
DnsLogMaxFileSize         : 10 MB (10,485,760 bytes)
DnsLogPath                :
DnsLogEnabled             : False

For my TransportService i do not appear to have an InternalDNSServers set. Is this typical or should that be set to my lab DNS server?

[PS] C:\Windows\system32>Get-FrontEndTransportService | fl *DNS*

ExternalDNSAdapterEnabled : True
ExternalDNSAdapterGuid    : 00000000-0000-0000-0000-000000000000
ExternalDNSProtocolOption : Any
ExternalDNSServers        : {}
InternalDNSAdapterEnabled : True
InternalDNSAdapterGuid    : 00000000-0000-0000-0000-000000000000
InternalDNSProtocolOption : Any
InternalDNSServers        : {}
DnsLogMaxAge              : 7.00:00:00
DnsLogMaxDirectorySize    : 100 MB (104,857,600 bytes)
DnsLogMaxFileSize         : 10 MB (10,485,760 bytes)
DnsLogPath                :
DnsLogEnabled             : False

For my FrontEndTransportService I don't appear to have anything set! I'm assuming that if I set my Adapter GUIDs to the correct values then the rest of the values will be picked up from my network card?

I will try it and post back!

Thanks for your help.

https://testconnectivity.microsoft.com - now passes an SMTP inbound test and mail mail is flowing again.For anyone else having a similar issue...

I used:

Get-FrontEndTransportService | fl *DNS*

to check the settings and then updated the internal and external adapter GUIDs and the External DNS server, then rebooted the exchange server. Still not sure if I need anything in the InternalDNSServers though!

Get-FrontEndTransportService | set-frontendtransportservice -externaldnsadapterguid "your guid here!"

Thanks for your help Andy.

May have spoken to soon... I had to add in the internal DNS server address for both the Transport Service and Front End Transport Service and reboot, then when it came back up again the Microsoft Exchange Mailbox Transport Delivery Service was not started... restarted that and mail... mail everywhere!