Under a default configuration, what is the simplest way to globally block mail from senderA@domainx.com?

The simplest way to globally block mail from a specific sender, such as senderA@domainx.com, under a default configuration is to add that email address to the Directories Profile Groups Blocked Senders list. This method allows for immediate action on incoming emails from that sender without the need to create complex policies or broader rules.

When an email address is added to the Blocked Senders list, the system recognizes it and automatically filters out any messages from that address across the entire network. This is an efficient and straightforward approach, as it requires minimal configuration and can be done quickly.

Blocking an entire domain, as in the option related to all senders in domainx.com, would be a more drastic measure than needed if the goal is to block a single sender, while creating a separate policy for just one sender may introduce unnecessary complexity and management overhead. Blocking based on IP address is typically less effective and more challenging to manage since IP addresses can change and may not be unique to the sender.

By choosing to add the specific email address to the Blocked Senders list, you ensure a targeted approach that efficiently achieves the objective with minimal effort.