1. From the Admin console, go to Appsand thenG Suiteand thenGmailand thenAdvanced settings.
  2. Scroll to the Attachment compliance setting in the Compliance section,
  3.  Hover over the setting, and click Configure or  click Edit or Add another.
  4. For each new setting, enter a unique description.
  5. Select email messages to affect
  6. Add one or more expressions to specify what's searched                                                                                                                                                                                                                                            - -  From the list, specify whether any or all conditions
  7. Click Add.
  8. From the list, choose what you want to specify for the expression: File type, filename or message size 
  9. Click Save. You might need to scroll to see it.
  10. Specify what happens if expressions match :  modify, reject, or quarantine
  11. Optionally Use address lists to bypass or control application of this setting
  12. Click Add setting 
  13. Click Save At the bottom.