You can have much more control like - color, font, content etc versus outsourcing this work. 

Google doesn't care about the font though in their SEO analytics. 

@Brian Garlington My advice is how I handle it, not looking for 1000 people to debate me on my method, it has worked for me for over 20 years, LOLFrom the spot you are in right now with them not responding and you believing they have moved I would post a letter on the font door that says the following in BIG BOLD TEXT______________                                                                ATTENTION (TENANTS NAME)Per our last conversation you  were moving out and would no longer be Occupying this property.

Let's say that the leases in place stretch 2 and a half pages with large font and double spaced with headers.

Keep paragraphs short- indent, make it easy top read- use the easiest font to read min 12 point font- serif font   Use bullets that are Easy to read               Nice and Large Body that looks appealing and Easy to read- CLEAN         Keep the message focused on the points at hand- BE CLEAR           Repeat the main point in different ways so that the message sinks in                           Offer proof with scientific data or testimonial and or some kind of Guarantee that they will not lose anything   Use testimonials- present proof that others have used                           SENSE OF URGENCY- if they don’t respond- thye will suffer a loss- money prestige or opportunity     Irresitable offer with a limited time to call           They need to call RIGHT NOW if they put that letter DOWN- they are not calling                       FEEL OF THE LETTER- enthusiasm-the "Main Idea tha tyou are pssionate about the letter needs to come off the letter   We care- what is the feeling that we impart into our product or service       What is your big idea, that you feel compelled to tell people abouit and that enthusiasm is what breathes life into the letter The letter is your one-on-one sales person           what is it that we love about what we do and makes us standout from the competitoin.    

I'm going to send out my first yellow letter campaign soon and I'm wondering which color font I should go with.

Sorry it is much harder to scan through the forum posts because of the "posted by" or "in forum" line underneath with a similar font and size.

You could try handwritten font which works well for me.  

It is also font loaded.  

Side note example: I have been running a clothing company for the past decade, and I can tell you that there was a few solid years between 2012-2016 where so many newbies came from no where thinking they can start a clothing company just by sticking some basic font on a T-shirt, without understanding any logistics of production, design, distribution, etc.