Google may have just made email marketing even more effective, and more important to your maketing strategy. Thanks to a new feature Google unveiled this week, email is now part of the search experience.

What do you think of the new feature? Let us know in the comments.

“Sometimes the best answer to your question isn’t available on the public web—it may be contained somewhere else, such as in your email,” says Google’s Amit Singhal. “We think you shouldn’t have to be your own mini-search engine to find the most useful information—it should just work. A search is a search, and we want our results to be truly universal. So we’re developing a way to find this information for you that’s useful and unobtrusive, and we’d love your feedback.”

You can sign up for the field trial here. The first million people to sign up can use it for now (once they get an email confirmation from Google, which can take some time, and Google accepts them – some won’t make it in). It’s only accessible in English on Google.com with @gmail addresses, for the time being, and is currently not available for Google Apps accounts.

“We’re working on some even more useful features,” says Singhal. “For example, if you search for [my flights] we will organize flight confirmation emails for any upcoming trips in a beautifully easy-to-read way right on the search results page.”

It will be very interesting to see what other niche-specific features Google might add in the future. Whatever they may be, they could factor into your email marketing plan.

Earlier this year, Google consolidated its privacy policies into one main policy spanning across Google products. This enables Google to use data from one product across its other products (who knows where else Gmail messages might appear in the future).

Some Gmail users keep a whole lot of emails in their Gmail accounts. One of the main selling points of Gmail when it was unveiled back in 2004, was that it had a ridiculous amount of storage capacity, so you didn’t have to worry about deleting emails. That’s a lot of content that can pile up. Highly personalized content that may just be relevant to some of your searches, even if you’ve forgotten about it. Until now, it’s been behind a wall that Google was not accessing from search, even though it was a wall that Google always had access to.

Email marketers may want to consider how their messages could perform in the long term.

VatorNews just reported on a study from Monetate, indicating that email converts better than search and social combined. What effect will emails in search have? Any additional conversions from search would simply be the icing on top of the email cake. An added bonus.

Reporter Krystal Peak says the report found that “social converted at 0.59%, while search was almost 5X better at 2.59%.”

“The real winners are those troves of emails filling up all of our inboxes right now,” she adds. “Converting 4.25%, email deals are converting people to sales eight times better than social.”

That’s exactly my point. Those emails that would otherwise just be filling up your inbox, most likely never to be seen again, can now serve a new purpose, surfacing in search results.

While for now, it’s only in limited trial mode, it stands to reason that Google will open up this feature for broad use in time.

Obviously, email campaigns are going to hit much more than Gmail users, but that doesn’t mean Google’s competitors won’t look at incorporating similar features into their products. It’s not hard to imagine Bing doing this with their new Outlook.com email service, for example. And who’s to say that Google won’t partner with other email providers sometime down the road.

Either way, Gmail has over 400 million active users. It stands to reason that many of them are using Google Search. Depending on how many opt into Google’s new feature (assuming that it expands beyond the trial period), that’s potentially a lot of people your email messages could be reaching well beyond the send date, at a time when they’re perhaps even more relevant than they were on that date.

It’s something to think about. What do you think? Comment here.