Exchange SE Event 5016

Hi @CWATSON 

Thank you for posting your question in the Microsoft Q&A forum. 

If you're seeing Event ID 5016 Microsoft Exchange could not discover any route to connector after transitioning from Exchange 2019 to Exchange SE, it's likely due to outdated routing topology or connector ownership not updating in Active Directory.  

Here are some steps you may try to resolve it: 

1.Check Send Connector source servers  

Run this PowerShell in Exchange Management Shell:  

Get-SendConnector | fl Name,SourceTransportServers,AddressSpaces   

Ensure only active SE servers are listed. If the old 2019 server appears:  

Set-SendConnector "Connector Name" -SourceTransportServers "EXCH-SE01","EXCH-SE02" 

Confirm Transport components are active: 

Get-ServerComponentState $env:ComputerName -Component Transport,FrontendTransport

 If inactive: 

Set-ServerComponentState $env:ComputerName -Component Transport -State Active -Requester Admin  

Then restart the Transport service: 

Restart-Service MSExchangeTransport
Restart-Service MSExchangeFrontendTransport 

If IsScopedConnector is $true and servers moved AD sites, un-scope or create a site-local connector:

 Set-SendConnector "Connector Name" -IsScopedConnector:$false

 2.Rebuild routing tables   Force all servers to refresh topology:  

Get-ExchangeServer | foreach { Restart-Service MSExchangeTransport -ComputerName $_.Name } 

Enable routing table logging for deeper inspection: 

Set-TransportService EXCH-SRV01 -RoutingTableLogMaxAge 1.00:00:00 

 3.Verify mail routing and queues 

Get-Queue  

If you see queues in Retry, the connector route is still invalid. 

4.Validate AD connector objects 

Check connector objects in AD: 

Get-ADObject -Filter 'Name -like "*Send Connector*"' -SearchBase "CN=Send Connectors,CN=Transport Settings,CN=Organization Config,CN=Microsoft Exchange,CN=Services,CN=Configuration,DC=yourdomain,DC=com"

Ensure only current SE servers are listed. 

 5.If you are using Edge Transport or hybrid:

Start-EdgeSynchronization  
Test-EdgeSynchronization  
Get-EdgeSubscription | fl Name,Status 

 6.If the connector uses a smart host: 

Resolve-DnsName smtp.your-gateway.example.com  
tnc smtp.your-gateway.example.com -Port 25 

I hope this helps. 

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We had to recreate the Send Connectors after we adjust the MasterRouting server on in the ADSI.

What is weird is that the send connector still worked for 48 hours after transitioning to the new SE servers to begin with and then just quit.