In addition to the article explaining how to see if an article was sent to an alias, another way to do this and manage them is to use rules.
This can also be used to manage multiple email addresses from a single mailbox.
1. In Outlook, go to File > Rules and Alerts and Create a new rule:
2. Start from a blank rule and select "Apply rule on messages I receive"
3. The follow the steps in the Wizard making sure the rule runs when the alias email address is in the message header. In this case I am searching for "[email protected]", marking as important and moving to a folder called "Website Enquiries":
Then switch the rule on and choose if it needs running on existing emails.