Whitelist – Hotmail (Via Outlook)
To ensure that you receive emails from known addresses, add the email address to your Hotmail address book. Sign in to your account and do the following:
Check the junk mail setting to make sure that somehow the domain or an address from the domain does not appear in the blocked address or domains.
Here is a document of things to check.
Understanding the Safe and Blocked Senders lists
Add the address to your contacts. Hotmail will usually deliver emails from addresses that are in your Contacts.