Custom Receive Connector on Exchange 2019 not working properly

Question

In Exchange 2019, I recently created a new receive connector in EMS to allow anonymous users to relay. It’s configured only to allow a specific server to send messages. Messages destined for internal users are delivered. However, messages for external email addresses are not delivered. This is the error in the logs: Unable to relay recipient in non-accepted domain.
This hasn’t been working for a while, possibly since we installed Exchange 2019 this past summer. I removed the previous receive connector and created a new one in power shell with no success. These are the commands I used:

 New-ReceiveConnector -Name "Relay Out" -TransportRole FrontendTransport -Custom -Bindings 172.x.x.x:25 -RemoteIpRanges 172.x.x.x

 Set-ReceiveConnector "Relay Out" -PermissionGroups AnonymousUsers

 Get-ADPermission "Relay Out" -User "MS Exchange\Externally Secured Servers" | where {($_.Deny -eq $false) -and ($_.IsInherited -eq $false)} | Format-Table User,ExtendedRights

How do I allow the server to send to anyone?

Answer 1

I tried both the ip of the server and any which didn't work. I contacted a vendor who assisted me. I had to these commands to the new receive connector:

Set-ReceiveConnector "EXSERVER\Relay Out EXSERVER" -PermissionGroups AnonymousUsers

and

Get-ReceiveConnector "EXSERVER\Relay Out EXSERVER" | Add-ADPermission -User 'NT AUTHORITY\Anonymous Logon' -ExtendedRights MS-Exch-SMTP-Accept-Any-Recipient

Answer 2

@Steege
Hi,

New-ReceiveConnector -Name "Relay Out" -TransportRole FrontendTransport -Custom -Bindings 172.x.x.x:25 -RemoteIpRanges 172.x.x.x  

Does the ip address in "Bindings" belong to the specific server which you would like to allow to send messages?
It is supposed to be the ip address of the network adapters on the Exchange server.

If so,please change it to 0.0.0.0:25 or the ip address of a specific network adapter.
And see if the problem persists.

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