Hi @Rudolf Amarlapudi ,
Based on my understanding of your description, creating mail users for the external email addresses could be the best fit for your scenario. In this case, these external users can have both the external email addresses and the logon credentials in your Exchange organization to access resources. All messages sent to the mail users are routed to this external email address. When a mail user is created, the Email entry on the General Tab is filled up with the external email address:
For more details, you may refer to: Manage mail users.
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