Forum Discussion
Exchange 2016 Mail Flow is Not Working
We had issues with updating to a latest Cumulative Update and messed up our EMS and some Web Config. It seems our Exchange Server is totally bricked. So, we decided to boot our Exchange Server from backup. The backup was dated September 2025. Unfortunately, after booting up the September 2025 backup, we noticed that the internal and external mail flow is not working (our Exchange 2016 is Exchange hybrid configured). The outgoing emails are stuck in Draft folder. The following troubleshooting steps have been done to no avail:
-Checked if the port 25 is open -> This port is opened
-Check the network settings if the Preferred DNS Address points to the correct DNS Server --> It points to the correct DNS Server
-Modified the DNS lookup under Exchange Admin Center > Servers > DNS Lookups > Internal DNS Lookups --> Added the IP Address of the DNS Server
-Modified the hosts file under System32 > drivers > etc --> Pointed the IP Address of the Exchange Server to the FQDN of the Exchange Server
Currently, are not sure of the next steps to do in order to fix the issue. Any advice?
1 Reply
At this point, the most helpful next steps are to verify that all Exchange services are running, check that the Transport service starts without errors, confirm that your send/receive connectors still exist and haven’t lost their configuration, and make sure the server’s TLS certificate is valid and properly bound. It’s also important to review the event logs (Transport, MSExchangeFrontEndTransport, MSExchangeIS) for any configuration or authentication errors. If major components are corrupted, the safest and most reliable fix is usually to run a “setup /m:recoverserver” using the same Exchange build as the backup, which rebuilds the server roles without touching the databases. Given the age of the backup and hybrid dependencies, this recovery step often repairs the underlying issues faster than continuing to patch individual symptoms.
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