How Do I Stop The Drips For A Specific Lead?

When someone requests that you stop emailing them, you can handle that directly through your Home Value Leads Dashboard. 

From the Lead Dashboard, you can search for a lead by name, email address, or physical address. Once you found them, click on the lead's name. It may say "No Information Given" if they didn't put their name in, but you can still click on that. This will open up the Edit Lead page. On the right hand side at the bottom, there will be a section that says "Send Automated Emails". (see image below) There are 4 options here:

Send All Automated Emails - This is the default status for all new leads. They will receive all of the drip emails. 
Only Send Monthly Emails - This will stop all emails except for the monthly home value report update. This is ideal for people you already know. 
Do not Send Monthly Emails - The lead will still receive the normal drip emails, but will NOT send the monthly home value report update. Use this when the report is highly inaccurate. 
Do not send any automated emails - This option turns off ALL automated emails. You would still be able to manually email them, but nothing automated.