Custom button to send email template to specific email address

Hoping for some help creating a button on the Account detail page to send an email template to a specific email address (non-salesforce.com contact). Here's what I have so far:

location.replace('/email/author/emailauthor.jsp?retURL=/{!Account.Id}&rtype=003&p3_lkid={!Account.Id}&template_id=00XV0000000LxZx');

Can someone help me with the TO field parameter to include a specific email address?