How Gmail Spam Filter Works?


One of the primary reasons of why majority of people switched to Gmail, back when it was launched is that it offered superior spam fighting capability, other than 1GB of storage. Over the years, Gmail has refined its Spam filter technology and almost no email escapes its filter and land into inbox. Practically, I personally observed only 2-3 spam mails per month in my inbox amongst other hundreds of mails that I receive. So let’s see how Google has managed to achieve such a high accuracy and what elements comprises of its spam filter.

The Basic – What is Spam Filter?

Consider spam filter as a funnel. This funnel is the collection of various factors and algorithms that decides whether the message is legitimate one or not. The number of factors could be typically range between 10 to 50 and an alarm from even a single factor is more than enough to mark that message as spam.

How Spam Filter Works?

Whenever someone mails you a message, it is made to pass through a spam funnel. If the message satisfies the funnel filtering criteria, it lands in your inbox, else it is transferred to your spam folder. The funneling happens in real time i.e. just before receiving the message, Gmail applies spam filter to it. The funnel checks depend on various factors that we will study later on.

gmail spam filter

What comprises Spam Filter?

spam filter components

Spam filter is made of various factors which indicate the possibility of maliciousness. These factors depend on various actions/events such as –

1) Whenever Gmail system detects that the message has malicious links and trying to scam user through a phishing mail.

2) When the message is sent from unknown/unconfirmed sender who does not exist in any of your past interactions.

3) When you have already marked any such similar mail as spam beforehand.

4) When the message is in different language than the languages you will normally use.

5) When many people marked same message as spam.

6) When the message is sent from reported email id or banned server or lesser known domain.

7) When it has similarity to suspicious messages and proactive words like “Get Rich Quickly” or “Free Goodies” .

In Addition, if you are using Gmail for apps, then the admin (organization IT department) can also set policies to mark mails as spam from other organizations.

Difference Between Spam and Online Advertising?

Factors written above make us think that online advertising falls under spamming. But this might not necessary be true. If you have explicitly given your email address and permission to advertise, then it doesn’t become part of spamming. When you don’t ask for it and until it’s not familiar to you, it is spam.

A very thin line differentiates both of them, and it mainly depends upon your personal preference. For example, you gladly accept 2-3 minutes of commercials during TV breaks however you get annoyed with in-program advertising. The difference lies upto the point it becomes annoying it is spam else advertising.

Online advertising is necessary evil, which offsets the cost of all the freely available information. Spam, on the other hand, increases the associated cost.

And in case you are wondering on how to reduce the number of spam messages, then the answer is very straight forward. Do not publicly divulge your email address. Do not sign up or submit your email address to any other service available. Here are some other tips to escape spammers like using picture signature -> . Also, if you want to make sure not to miss some important message, then always remember to whitelist the sender.

As reported in our forum, recently Gmail has started showing information on why that mail was considered as spam. This is an appreciated step from Gmail team for informing and education users. Tell us in your comments some more experiences with spam messages.

Filed under Gmail Tricks. Posted by Abhishek and last updated on April 5, 2012.