This article explains the steps to take If your Organization require to customize Anti-malware Alerts for a Specific domain.
Email Security.cloud
In order to set a custom Anti-malware Alert for a Specific domain :
1 - Go to Dashboard > Services > Anti-Malware
2 - Click Apply to : Global settings and change it to Custom settings after selecting the domain
3 - Under Administrator Email , Type the Administrator to receive the Alert and click (+)
4 - Save and Exit
Note: If you will need to revert the changes so the Alerts must Apply to Global settings, You would need to revert the changes from the custom settings back to the Global as explain in (Step 2).