4 Things You Should Know About Gmail Spam Filter

Vladislav Podolyako
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Spammers are getting more and more devious in their attempts to smuggle their emails through the defense systems of your Gmail inbox. Luckily, so does the Gmail spam filter. In that case, ‘devious’ is not the right word. Think of ‘Harder Better Faster’ by Daft Punk.

And, just like in the song, its work is never over. Email service providers are responsible for tons of private data, including business correspondence, reports, financial information. Therefore, it’s their duty to keep up with cybercriminals’ shenanigans and constantly improve their defenses.

One may think that in the age of supercomputers and all the data at Google’s fingertips, how can it NOT succeed at creating a smart and competent spam filter? What’s so special about it?

Just think about it. Gmail is a part of a huge artificial mind that learns, explores, analyzes, and adapts. Having all the resources you need is not enough to make something that remarkable. To further emphasize the power of assets behind the Gmail spam filter, let’s try to deconstruct it.

1. Gmail was the first to combat image-based spam

Image spam was a big problem in 2004. You probably can remember all those annoying banners with bright colors, shapes, and fonts that came out straight out of WordArt. Ugh.
Since images were able to slip through defense systems, many spammers used them as a loophole for pushing their messages without being detected by content and language filters.

Naturally, when Gmail was introduced, many had concerns about spammers abusing the newly made email service just like they’ve done to other providers. What nobody (including spammers) expected, however, was that Gmail greeted incoming spam messages with Optical Character Recognition, effectively deciphering the text hidden within the images and sending it where it belongs — to the Gmail spam folder. Of course, while those features had their areas for improvement, Gmail was nonetheless successful at keeping a large part of their users’ mailboxes spam-free.


2. Gmail lets users decide what they want to receive

What is spam to you?

It can be an overabundance of ads. Lots of “Nigerian prince” emails. Fake “re:” messages. Emails with suspicious attachments. Or simply emails that you don’t like and don’t want to see anymore. When the context is so large, how can a filter figure out what to do?
This question got many spam filter developers flabbergasted. But Gmail was able to find a simple, yet brilliant solution.

Since spammers get more and more crafty, who gets to define what spam is? Users, of course! Knowing this, Gmail bases its key principles on user engagement.

That means that the Gmail spam filter carefully processes all feedback, takes all the cases when emails that didn’t seem to fit the “spam” type into account, and uses that data to improve its spam tracking and monitoring.

Therefore, if a considerable portion of mailboxes faces a new type of spam and flags it as spam, the Gmail spam filter will incorporate that information in its database. After this, whenever the new creation of spammers tries to find its way into other inboxes, it will be intercepted by filters and redirected to the Gmail spam folder.

In addition, the way your recipients respond to incoming emails defines the fate of your Gmail inbox and is crucial to creating business leads. If you send emails only to willing subscribers and your targeting is correct, your domain reputation grows whenever the users open and read your messages. However, each time a user moves your email to spam or adds it to the blacklist, your domain reputation drops, and the Gmail spam filter starts being too aggressive and treating you with suspicion. In the end, you may even be banned from sending emails until you fix your reputation.

This is how Gmail ensures that all users receive only the emails they expect and want to read. Such was the core essence of Gmail’s anti-spam system and it remains till that day. In our opinion, it’s the ability to let users participate in building superior measures against unwanted emails that made the Gmail spam filter so effective.

3. Gmail keeps up with the escalation of spam attacks

While it sounds like a basic requirement for every functional email service provider, it’s still a ton of work only a truly competent team can pull off. Since 2004, people have come to rely on Gmail as their main defense against malware, viruses, cyber threats, and all kinds of phishers and scammers. It’s a large responsibility — and an even larger amount of resources.

And let’s not forget that we live in a time when even the largest titans are not protected from data leaks, loss of financial assets, and spammers keep tweaking their software to explore and abuse all vulnerabilities in the defense systems.

So, how does Gmail keep up with those threats and expectations?

Research and forecasting. Yes, we’ll never get tired of bringing up the importance of research. Everybody does it. Even Gmail. Its anti-spam team is on the constant watch for new dangers — as well as the means to combat them. Moreover, with the use of Deep Learning and data analysis, Gmail is able to thwart over 3% of attacks on your inbox and private data because it can predict how and when they will happen!

Artificial intelligence and deep learning. Gmail invested a lot of time in A.I. and Machine Learning to design the techniques that would create an intelligent anti-spam system, capable of adapting to new threats to email security. These smart classifiers are able to categorize all incoming spam, study their characteristics and general features. Then, they use that data to prevent any future spam attacks. By using the data gathered from the most recent spam attacks, it creates and runs through various phishing/spam scenarios, calculates what tricks spammers would be inclined to use or how their behavior patterns will change. To pull that off, a defense system must process huge chunks of data.

Monitoring and more monitoring. Simple as that. Regularity and knowing how to look for threats and where to look for them are the signs of a truly advanced anti-spam system. On a daily basis, Gmail scans over 90% of attachments and emails for spam, to ensure that nothing slips past its defenses and threatens your private data.


4. Gmail’s immune to abuse

It may sound like something straight out of the comic books, but it’s hard to deny the facts. Being well aware of the spammers’ ability to exploit various blindsides or loopholes in anti-spam filters, the Gmail team made sure that in their case, there is nothing that can be abused or used against them.

How did they do this?

By not relying on one feature alone. Gmail machine learning is designed to work with images and text. However, how do they handle spoofing? Does delivery fail spam? Fake social media notifications?
This is where many other assets come to the rescue:

Gmail uses advanced IP address tracking to see where suspicious emails come from, scans these sources across numerous blacklists, and blocks them if it’s necessary.

Sophisticated behavior tracking allows Gmail to catch suspicious patterns that spammers are bound to demonstrate in their targeting, mailing method, and email settings.

Rate limiting features prevent suspicious senders from sending tons of emails to Gmail users’ inboxes. It buys Gmail sometime before it analyzes all the messages and takes necessary measures for protecting users.

In case when there is an obvious threat, Gmail can literally shut down the suspicious domain and block it from sending emails, interrupting the entire process of delivery. This is why lots of spammers won’t risk using Gmail for sending emails.

To help AI/ML classifiers, Gmail uses automated Tensor Flow filters that sift through large volumes of incoming traffic, fishing out hidden spam, and masked dangerous content. This sophisticated feature allows Gmail to process over 100,000,000 of spam messages every day, ensuring that none of those emails go to your inbox. The same technology keeps you safe from phishing scams and malware.



We’re not likely to see the end of the war between spammers and email service providers. This is the price we have to pay for all the amazing opportunities brought to us by the internet. However, Gmail remains to be proof that it’s possible to hold your ground against spam attacks by combining artificial intelligence and multiple human experiences. Gmail continues to grow and evolve because it stays connected to its users. Their vision and perception shape its approach to spam — and the means of stopping it.

In our opinion, there is much to learn from the inner works of Gmail, both in terms of your outreach and your work in general:

Stay tuned to your clients’ experience. Whether you work in B2B lead generation marketing or B2C, disconnecting yourself from your target audience leaves a gaping hole in your defenses, not to mention your roadmap. Whenever you let marketers and analysts tell you what your potential buyers think and don’t bother to ask your buyers, you remain blind to opportunities or weaknesses. Your competitors won’t hesitate to exploit it.

Use more than one feature to protect you. Whenever a tool is promoted to you as “all-in-one”, it’s quite likely to be the Jack of all trades, master of none. But it’s the master you need. After all, if you want high-quality protection, high-quality sales development, high-quality design, you don’t hire one person to cover all these tasks. You seek several experts that are experienced in their area. Your choice of tools and software should be based on the same principle.

Think forward. It feels nice to be comfortable with what you see and do. But the feeling of comfort can also be deceiving. It lulls you into a false sense of security and stability, making you sit still when it’s time to move and act. So, don’t sit still. Don’t be satisfied with what you currently have. Look into your stats and data, and see what you should do to keep going — or what kind of risks may arise in the not-so-distant future.

We hope you enjoyed dipping into the incredible world of Gmail. In case this piece left you curious for more insights, you can become our subscriber — because we don’t send unsolicited newsletters! We share updates with our willing and engaged readers. Want to join us? It takes just a click. 

Vladislav Podolyako

Vladislav Podolyako

Co-founder and CEO of Belkins and Folderly
Vlad’s decades of entrepreneurial wisdom and business building experience have allowed him to successfully mentor a diverse group of business owners, entrepreneurs in growing their companies. A recognized expert in the areas of transforming organizational culture and leadership development, B2B Sales, Marketing, spent more than 10 years building technology products, with a background in communication networks and electronic device engineering.
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