Exchange 2016 not able to receive external emails but Can Send externally

Hello,

I have an issue that I have been struggling with for the last few days.

We have exchange 2016 installed on windows server 2012 r2 physical box and we have an Edge Server installed on a windows server 2012 r2 physical box.

We are able to send and receive emails internally and we are able to send emails to other domains (Externally) but we cannot RECEIVE emails.

When I check the mail queue on the EDGE server I see the mails that were sent from outside our network either in Queue ready to be sent or with the following errors

SmartHostConnectorDelivery 451 4.4.0 DNS query Failed The error was DNS query failed with error ErrorRetry

DnsConnectorDelivery 451 4.4.0 Dns query Failed The Error Was: DNS query Failed with error InfoNoRecords

DnsConnectorDeliver LRT = 10/29/2017  ; LED = 441 4.4.1 Error encountered while communicating with primary target ip Address "etc"

Any advice?
Chris BlanksAsked:
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Valentina PerezExchange ServersCommented:
Hi Chris,

What did you change in your environment?

Check the event logs..do you have any error related to transport?

Regards
Valentina
RicheyyyCommented:
Looks like an external dns issue. Have you checked you web designers haven't migrated you to a new server and not populated settings or fiddled with something?
Wasim ShaikhCommented:
Looking at the error it seems to me that Edge Server is not able to resolve Exchange Server, The DNS entries must be correct for resolution to be successful.
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AlanConsultantCommented:
Hi,

1)  Have you tried rebooting the Edge Server?  Always worth asking :-)

2)  If you log on to the Edge Server, and ping the Exchange Server by hostname, does it respond?

3)  Please can you run an IPConfig /All on the Edge Server and post the results.

Thanks,

Alan.
Hemil AquinoNetwork Security EngineerCommented:
SmartHostConnectorDelivery 451 4.4.0 DNS query Failed The error was DNS query failed with error ErrorRetry

DnsConnectorDelivery 451 4.4.0 Dns query Failed The Error Was: DNS query Failed with error InfoNoRecords

I had this problem before, here is what you need to do:

1- Make sure you dont have any external DNS in you exchange server such as: 8.8.8.8 4.2.2.2
2- Login to ECP panel and click on Server> select server name> DNS lookup and make sure you have the right DNS. Attached my image
DNS-EX.png


3-  Also, try changing your DNS sever IP if the problem still persisting, I had an experience that something was going on with the 8.8.8.8 and it couldn't resolve any name so I had to use other server IP and them bam it worked.

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AlanConsultantCommented:
Hi Chris,

Any update on the suggestions and queries above?

Thanks,

Alan.
AlanConsultantCommented:
Solutions identified.
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