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Hello,
We are in the process of co-existence configuration with Exchange Online and On-Premises messaging and On-premises gateway Cisco IronPort. When we send out emails using connector from Exchange Online to On-Premises. Ironport log shows that as incoming DNS hostname as example: "mail-mw2nam04lp2168.outbound.protection.outlook.com". This is generic any other domain from Exchange Online outside our tenant would appear coming from similar mail-mw2nam04lp2168.outbound.protection.outlook.com
Is it possible that messages from our company's tenenat "Exchange Online" it appears as "Company-com.mail.protection.outlook.com" as this same address we are using to send emails from On-premise to Exchange Online? In this way on email gateway, we could see difference between emails originating from us (our company) or anyone else using Exchange Online?
Thanks
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Just wanted to check if the answer shared below helps. If this was helpful, please consider marking "accepted answer" as this will help others in the community as well.
Hello Raman03
Do you mean configure Exchange Online to use a custom sender domain for outbound emails?
https://learn.microsoft.com/en-us/microsoft-365/admin/email/change-email-address?view=o365-worldwide
Regards
Shaofan