A Sender is not exempted from Email Impersonation Control scan despite adding the sender address to the Approved Sender list in Email Impersonation Control configuration.
The Email Impersonation Control service looks at the Envelope "Mail From" address at the time of scan and not the "Body From" address.
The "Body From" address is the sender address visible to the end user while opening a message in an email client. The actual sender or the "Mail From" address is not always same as the "Body From" address.
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Note: Any changes made to the Email impersonation control configuration takes an hour for propagation.