A Marketer’s Field Guide to Gmail Inboxes
Gmail has had a relatively short life compared to the other large webmail providers such as Yahoo!, Hotmail and AOL. Gmail launched in beta in 2004, became available to the general public in 2007 and officially launched out of beta in July 2009. According to our research Gmail closed 2010 with 193 million users, which is less than Yahoo! and Hotmail, but it is adding new users at a much faster rate than these two providers.
Google and its Gmail division march to their own beat. Unlike many of its large competitors, Gmail doesn’t provide feedback loops, whitelists, disclose use of public blacklists or provide a lot of direction, tools or support for senders. The company posts some rough guidelines for bulk senders but these are generic recommendations that apply to just about any ISP.
Gmail, like the rest of Google’s products, was designed by a bunch of really smart engineers whose goal is to develop intuitive, efficient and useful products. And like the rest of Google’s products, their email filtering technology and methodologies are kept very close to their vest. The only thing we know for sure is that their filtering is primarily based on its users’ actions.
User base profile. We picked up some great demographics on Gmail users from hunch.com. According to their study: Gmail users are most likely to be thin young men ages 18-34 who are college-educated and not religious. Like other young Hunch users, they tend to be politically liberal, single (and ready to mingle), and childless. Gmail users live in cities and have traveled to five or more countries. They’re career-focused and plugged in — they mostly read blogs, have an iPhone and laptop, and listen to music via MP3s and computers (but they don’t have a DVR). At home, they lounge around in a t-shirt and jeans. Gmail users prefer salty snacks and are introverted and entrepreneurial.
Spam filtering and sending reputation. Gmail primarily uses its community of users to determine whether email is spam or not. Reputation is based on a sliding score of 0 to 100 with 100 being the best score. The reputation score at Gmail indicates the probability that a given sender’s mail is not spam. So, if the reputation score is high, Gmail feels confident delivering more of that mail to the inbox.
Like most reputation systems, the foundation is user reports of ‘spam’ and ‘not spam’. As email arrives, Gmail measures how many times email is automatically delivered to the inbox or the spam filter and how many times a user manually reports an email as spam or not spam. A formula taking into account these four actions is then used to calculate the sender’s reputation that will determine future deliverability. Of course, not all user reports are considered equally. The reputation system only uses the reports of a subset of users – those who they believe will provide the most useful information for the system.
Inbox delivery is also impacted by content filtering. Gmail does sophisticated content filtering, scouring the content of the email headers, body, and attachments for key words, images, HTML, URLs, malware, and other spammy components.
As an aside, it’s important to understand that although Google owns both Gmail and Postini products, each service utilizes its own unique proprietary filtering technology. Postini is a B2B spam filtering solution used primarily by businesses to manage their enterprise mail. Postini (industry insiders occasionally call it “Houdini”) is more mysterious then Gmail in some ways. If you find your mail getting stuck in Postini’s spam filter, Google provides a Message Analyzer that allows senders to examine the tags inserted into an email header to help decipher the reasons for the quarantine. You may find a hint of the filtering issues via the Analyzer but the only way to figure out how to get through this filter is to constantly test different email content.
Feedback loops. Sorry, there are none. The only thing Gmail offers that may help offset complaints is the list-unsubscribe header which enables webmail functionality that makes it easier for a user to request to be unsubscribed from your list. In the absence of a classic FBL, it is especially important to remove inactive users from your list to ensure that you’re not sending mail to people who don’t want it and might be reporting it as spam.
Whitelisting. Gmail does not offer a whitelisting service nor do they subscribe to any third-party whitelists.
Prioritized delivery and Engagement. The Gmail Priority Inbox feature was launched in September 2010 and allows users to identify and prioritize that email that is most important to them. One of the drivers behind this feature is the emergence of what’s called email “bacn”. This is the email that lies somewhere between email from your friends and family and the blatant spam that ends up in your bulk folder. Bacn is comprised of newsletters, coupons and advertisements that you have legitimately opted in for. Adam Sutton from MarketingSherpa recently posted a blog called Getting into Gmail’s Priority Inbox. In this article, Adam deciphers some of the key features and calculations behind Gmail PI. We don’t have specifics on if/how Gmail is considering PI users’ decisions into its filtering algorithms but you can be guaranteed that it will be eventually.
Sending Infrastructure requirements. SPF and DKIM authentication should be implemented. Be sure that your From: domain matches the d= in your DKIM record. Senders using shared IPs at ESPs should sign DKIM with their own unique signing domain. For example, one should be signing mail with something like d=esp.client.com instead of d=esp.com. If for some reason you are not authenticating then Gmail creates a “best-guess” record using a combination of record lookups to match your sending IP with your domain to authenticate your email.
Gmail does not disclose explicit use of specific public blacklists (PBLs). However, our research does show a correlation between bulking at Gmail for those IPs listed on the most popular PBLs like Spamhaus.
Partners. Gmail does not have any partner domains that we are aware of – no surprise here. Gmail does host an increasing number of small business domains and a few small ISPs.
That’s it for Gmail. Stay tuned for the next blog in my Email Marketer’s Field Guide series!
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About Melinda Plemel
Melinda has been working at Return Path for 9 years and is currently the Senior Industry Advocate and is responsible for managing global partners that join Return Path's Data Exchange program and emerging markets. She is the key to helping and educating Return Path on mailbox providers, anti-spam, and email technology trends, as well as to educating receivers about everything Return Path has to offer.