Answer:
Configure a safe sender
Step-by-step explanation:
The Safe Sender List in Outlook, is a list of domain names and email addresses that are not managed in the manner spam and junk messages are filtered out and placed in the spam or junk folder. The emails of contacts added to the Safe Senders list are always received in the inbox
Therefore, to ensure that messages from his colleague are never treated as spam, Walt should;
Configure a safe sender.