If you are preventing a specific user from receiving email alerts, you need to disable the alert or modify the recipient address to prevent a specific administrator from receiving the alert.
You can try the following steps:
1.Log in to Microsoft Defender as an administrator.
2.Find “Email & Collaboration” in the left navigation bar, go to “Policies & rules” and select “Alert policy”.
3.Select the policy you need to modify. You can disable this policy to prevent all administrators from receiving e-mail alerts. Or modify the recipient's e-mail address to exclude a specific administrator.
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