In a hybrid environment I'm not able to send email from a company's Office 365 account to an on-prem account.
All other mailflow seems to be working ok.
When I send an email from an online account (e.g. cloudaccount@myorg.com) to an on-prem account (e.g. onpremaccount@myorg.com) .
The sender gets an NDR which starts with the following:
Delivery has failed to these recipients or groups:
ONPREMACCOUNT
Your message wasn't delivered because the recipient's email provider rejected it.
Diagnostic information for administrators:
Generating server: SIXPR06MB159.apcprd06.prod.outlook.com
ONPREMACCOUNT@MYORG.COM
Remote Server returned '< #5.7.0 smtp;550 5.7.0 Proxy session setup failed on Frontend with '554 5.4.4 SMTPSEND.DNS.NonExistentDomain; nonexistent domain'>'
When I do a trace from within the EAC it shows me the following event for that particular email:
RECEIVE - Message received by...
SUBMIT - The message is awaiting submission to the mailbox store.
RECEIVE - Message received by...
FAIL - The message was not delivered.
Is there anything I need to change in the on prem Office 365 receive connector?