Below are the steps to set up a mail flow rule to bypass Spam filtering.

1. Create a new mail flow rule in your Microsoft 365 Exchange Admin Center.
2. Give the rule a name, e.g. Spam bypass.
3. Click Add rule > Create New Rule.
4. Select a name for your rule.
5. 'Apply this rule if - The sender - IP address is in any of these ranges or exactly matches'. Enter the appropriate IPs for your tenant which can be found in the below article: MetaCompliance Mail Server IP Addresses - All Data Centres – MetaCompliance
6. 'Do the following - Modify the message properties - Set the SCL' > Select Bypass Spam Filtering.

See example below: