Start a new email within Outlook.

Drag the Spam/Phishing email from your list of emails and drop it into the new email. Address the email to [email protected] and put Reporting Spam/Phishing as the subject.

Finally you should see the email you made with the spam/phishing email in the Attached section.
Attaching Spam as an Attachment for Outlook 2010 & 2013 (Windows)
Create a new email and address it to [email protected] with the subject of SPAM Email.
Click on the Attach Item icon and choose Outlook Item from the drop down.
In the Insert Item window, find the email you would like to attach. Below the OKĀ button ensure that it is send as attachment. Click OK.

The email should now show an attachment. Click Send.