Email marketing experts recommend that you always ask your subscribers to “please add me to your address book” on your opt-in thank you pages and your welcome emails to prevent spam filters from blocking your emails.

It’s good advice.

MailChimp is taking that idea slightly further by including an “Add-to-Address-Book” link to your email campaigns and opt-in process.

We’re using microformats (an emerging technology being used more and more in “Web 2.0″ apps) along with a little dose of good old fashioned vCards…

Here’s how it all works.

Whenever someone signs up for your list, they’re taken to your “Thank You” landing page. Below is an example:

In the footer of that landing page is your List Contact Information. You plugged this contact information in when you created your MailChimp list, so there’s nothing extra you need to do.

This contact information has embedded hCard microformat code around it, which basically makes it “readable” to browsers and plugins that recognize microformats, and can then “do” something with it (here’s an example of how Google Maps uses microformats).

The little orange icon links subscribers to your vCard (which we automatically create and host with every list you setup in MailChimp). When they click the link, your subscribers are prompted to add the vCard to their default address book program (Apple’s Address Book, Outlook Addres Book, etc).

We also add vCard attachments to your initial list opt-in welcome emails to make it easier to get into address books (but we don’t add them to your regular email marketing messages).

And we’ve taken the contact information that we automatically add to your email footers and embedded it with hCard microformat code (for every email message you send).

Not A Silver Bullet Yet.

Just to set your expectations, this technology isn’t going to significantly boost your deliverability or findability—yet.

Microformats have been around a few years. Nevertheless, it’s an emerging technology, so you’ll still need to politely ask your subscribers to “add me to your address book.” Mark Brownlow recently pointed to this handy tool that automatically generates whitelist instructions that you can embed on your website. Just build your instructions, save the page to your site, and add the link to your MailChimp opt-in pages.

But as more and more browsers and web apps support microformats, you’ll see all kinds of cool ways this technology can be used.

This is just one little way MailChimp is keeping your email marketing ahead of the curve.

P.S. There’s an interesting article over at Digital-Web about the potential of microformats (non-techies should just scroll down and start reading at the “Aggregators” section).