This is especially useful when you have contacts that sit outside your domain, e.g. for those with @barberofsheffield.co.uk at the end of their email address, will not see those with @christiesdirect.com in their Global Address list.
Therefore, you can easily add them to your contacts in outlook so they are always there when you search.
Simply double click on the person's email address and you will see three dots to the right hand side
Click on these and then click 'Add to Contacts'
You will then be presented with the below screen, simply click Save & Close if the detailed entered below are correct.
To add these contacts to an email, click on 'To', you will see the below screen, change the 'Address Book' to Contacts and you will then see all the contacts you have saved.
To view your contacts at any point, just click on this icon in your Outlook