Hybrid Mail Flow

Question

Hello everyone,

I have an Hybrid environment with E2K13 servers.
My mail flow is, for outgoing messages:
From On Prem Mailbox to Internet:
Mailbox -> Edge Server -> EXO -> Antispam-> Internet
From EXO to Internet:
EXO -> Antispam-> Internet

SMTP domain: @test .com
I have hosted an application at AWS that contains a subdomain email address @aws .test.com.
The MX for that subdomain is on AWS.
When I send an email to x@aws .test.com from OnPrem mailbox I receive an message "Remote Server returned '554 5.4.6 Hop count exceeded - possible mail loop'. It´s not working when sends email from EXO.
I added @aws .test.com as Accepted Domain in On Prem and EXO but not working:
New-AcceptedDomain -DomainName aws.test.com -DomainType InternalRelay -Name aws.test.com.
Any clue?

Any help will welcome.
Thank you all.

Answer 1

What antispam are you using? Please note that if you are using 3rd party anti-spam filter, it can only filter the messages sent from Internet to your organization, detailed information about this: Manage mail flow using a third-party cloud service with Exchange Online, you could try temporarily disabling the antispam to verify whether the issue is caused by this.

In addition, here is an article discussed about Fix email delivery issues for error code 5.4.6 or 5.4.14 in Exchange Online

Answer 2

Your anti-spam solution is configured to route all messages sent to your domain to your Exchange org and creating a mail loop. You will need to set an exception for aws.test.com and route it to AWS.