You can easily create a new Matter from your Outlook, using the Thread for Email Outlook add-in.
Select any email and open the add-in using the steps here. Click on Create new Matter.
Enter the details for your new Matter.
Choose the main client for this matter either from the contacts in the selected email, or any existing contact in Thread. If searching Thread contacts, start typing the name to find your contact.
To choose a contact from the email, the contact must already be an existing contact in Thread. See steps here for creating Thread contacts via Outlook add-in.
A message will show at the top saying the matter was successfully created.