Hi, @IniobongNkanga-8038
Thanks for posting your question in the Microsoft Q&A forum.
Based on your description, your organization's email system may be under spoofing attack, where attackers send emails that appear to be from trusted sources. Both phishing and spam are somewhat deceptive, and it does not mean that the administrator's account cannot send spam.
If you want to improve your organization's anti-phishing protection, you can refer to this link:https://learn.microsoft.com/en-us/defender-office-365/anti-phishing-protection-tuning?source=recommendations
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