We have an application sending emails. It always works for domain addresses that are in o365. It fails every time to external addresses. The application is from a local server on prem and uses a mailbox in o365. Looking at the message tracking logs,
I get this
'[{LRT=};{LED=550 5.7.64 TenantAttribution; Relay Access Denied};{FQDN=};{IP=}]' |
The receive connector on my local exchange server has the IP address for the application server in the Remote Network Settings.
What else can I check?