What is the best way to ensure that all mail from marketingcompany.com is not greylisted, but still undergoes spam scanning?

The best approach to ensure that all mail from marketingcompany.com is not greylisted while still undergoing spam scanning is to implement a greylisting policy set to "Take No Action," specifically scoped from marketingcompany.com to internal addresses.

This policy effectively avoids any delays caused by greylisting for incoming emails from the specified domain. By setting the action to "Take No Action," you ensure that emails from marketingcompany.com are accepted and processed immediately, bypassing any greylisting mechanisms that could hold these messages temporarily. However, because the scope is configured from marketingcompany.com to internal addresses, it allows these emails to still be subjected to the spam scanning process, ensuring that any malicious or unwanted content is filtered out.

This balance of not greylisting the domain while maintaining spam protection is crucial for maintaining email flow and safeguarding the inbox.

The other choices, while valid approaches in different contexts, either do not meet the requirements as effectively or might compromise security by not including necessary scanning processes. For example, whitelisting the entirety of marketingcompany.com would completely exempt the domain from spam scanning, which could pose a significant risk.