I can totally understand your situation but the only thing you can do now is to fill out the form and email back. For more information, you can refer to the paragraphs If I am a website owner, how do I correct a warning on my legitimate site? and If I am a website owner, what can I do to help minimize the chance of my website being flagged by Microsoft Defender SmartScreen? in this doc.
Besides, another thing you can try is that if your organization has a Microsoft support plan, you can open a support ticket on this page, clicking "Create a support request".
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