I have an new hybrid connection between Exchange 2019 and O365. Mailrouting inbound and outbound (CMT) through onpremise Mailrelay.
Only one testuser are already migrated to O365.
After some testing I found in O365-Messagetrace many Mails to external recipients. These mails are coming from the puplic-IP from the Mailrelay and where sent to recipients they are also in O365 (recipient-mx pointed to O365). Other recipients (google, gmx.....) where sent directly.
All mails should be sent from mailrelay to external and not through own O365-Tenant. The O365-Messagetrace should only be shown internal Mails for my understanding...
I hope this is understandable :)