Hi,
You can check this article.
https://learn.microsoft.com/en-us/microsoft-365/security/office-365-security/configure-your-spam-filter-policies?view=o365-worldwide
Enable or disable anti-spam policies
You can't disable the default anti-spam policy.
In the Microsoft 365 Defender portal at https://security.microsoft.com, go to Email & Collaboration > Policies & Rules > Threat policies > Anti-spam in the Policies section. To go directly to the Anti-spam policies page, use https://security.microsoft.com/antispam.
On the Anti-spam policies page, select a policy with the Type value of Custom anti-spam policy from the list by clicking on the name.
At the top of the policy details flyout that appears, you'll see one of the following values:
Policy off: To turn on the policy, click Turn on icon. Turn on .
Policy on: To turn off the policy, click Turn off icon. Turn off.
In the confirmation dialog that appears, click Turn on or Turn off.
Click Close in the policy details flyout.