FQDN in sentconnector don't work


i'm from germany and try to explain my exchange problem.

First i will tell you some about my environment.
2x DC running on W2K16
2x Exchange 2016 running on W2K16 in a DAG

I want use our Proxmox Mailgateway as smarthost.
When I enter the IP of the smarthost, everything is fine.
But i want use the FQDN because this name will be used soon in about 20 exchange servers.
There will be an error in exchange queue:
26.02.2018 15:01:27 - Server at mailrelay.mydomain.int returned '451 4.4.0 DNS query failed. The error was: SMTPSEND.DNS.NonExistentDomain; nonexistent domain mailrelay.mydomain.int -> DnsDomainDoesNotExist: InfoDomainNonexistent'

In cmd console on exchange and dc i can use nslookup and the result is ok.

Why can't the exchange resolve the FQDN when i use them as sent connector?
Where can I look for errors execpt the event log?

I hope you can help me :-)

Best Regards,
P KIT-AdministratorAsked:
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did you created DNS A record for your smarthost?
P KIT-AdministratorAuthor Commented:
Yes, the DNS domain "domainA.int" is hosted by the firewall. This DNS Server is a resolver for multiple DCs.

The DC Domain with the problem is like "domainB.int". The DNS of the DC is forwarded to the firewall DNS. Resolving the FQDN "mailrelay.domainA.int" is successfull.
is this smart host fqdn is published internally or it is published ?
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P KIT-AdministratorAuthor Commented:
only internally
you mean to say you are just going to use your smart host for internal emails?

you will need to have public DNS record for your smarthost.

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P KIT-AdministratorAuthor Commented:
oh ok, so i can't use an internal smarthost with internal FQDN that can resolved?
reason is that whatever emails going outside of your organization are public domains with public DNS records.

connector works on multiple parameters. One parameter is DNS lookup while sending emails out.

So your smart host should have Public FQDN with Public DNS records published. Else it will keep failing with DNS failures .
P KIT-AdministratorAuthor Commented:
oh ok, so i have to use the ip-address :-(

Thank you, for your help! :-)
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