Gmail Spam Filter: When It Is Not Enough to Stop Spam

Gmail spam filter is a mostly invisible part of the popular free email service developed by Google, but it plays a much more important role than most people realize. However, there are cases when it is not enough to stop spam, which is where third-party email organization tools such as Clean Email come in.

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What Is Gmail Spam Filter and How It Works?

Did you know that it takes the average person five seconds to identify and delete a spam message? Considering that most office workers receive around 100 emails every single day, it’s easy to see just how mind-bogglingly high the productivity cost of spam really is.

Fortunately, Gmail users are not defenseless when it comes to spam because Gmail spam filter always has their back. You can think of Gmail spam filter as a stacked funnel that takes into considerations a number of factors to determine whether an email is legitimate or not.

To start with, Gmail spam filter always checks whether the sender’s email address has been blacklisted before. If it has, it won’t let the email in no matter what. But what about emails coming from unknown senders? That’s where things get more interesting.

Gmail maintains a massive database of malicious links, and Gmail spam filter looks for them when analyzing incoming emails. In addition to links, the filter is also able to detect suspicious phrases and words, such as “Viagra” or “online pharmacy” or “how to make money online.” Spelling mistakes and bad grammar are other tell-tale signs of spam.

Spammers are, of course, aware of the capabilities of Gmail spam filter, and they are constantly inventing new ways how to circumvent it. For example, they are substituting certain characters (v1cadin for s4le) or crafting spam messages that seem completely legitimate to anyone without many years of industry experience.

To maintain the upper hand, Google has been using artificial intelligence and its in-house machine learning framework, TensorFlow, to help train additional spam filters for Gmail users. Thanks to AI, Gmail can now block an extra 100 million spam messages every day.

“At the scale we’re operating at, an additional 100 million is not easy to come by,” says Neil Kumaran, product manager of Counter Abuse Technology at Google. “Getting the last bit of incremental spam is increasingly hard, [but] TensorFlow has been great for closing that gap.”

How to Change Gmail Spam Filter Settings?

As we’ve just explained, Gmail spam filter is very complex software that doesn’t require basically any attention to work as intended. You can, however, change some Gmail spam settings to tweak it to your liking.

Bypass Spam Filters for Messages from Addresses or Domains

For example, you can bypass spam filters for messages from addresses or domains specified in an approved sender list:

  1. Sign in to your Google Admin console.
  2. Go to Apps → G Suite → Gmail → Advanced settings.
  3. Select an organization.
  4. Scroll to the Spam section, hover over the Spam setting, and click Configure.
  5. Check the Be more aggressive when filtering spam box to configure more aggressive spam filtering.
  6. Check the Bypass spam filters for messages received from internal senders box to bypass spam filters for internal messages from users within the same organization.
  7. Check the Bypass spam filters for messages received from addresses or domains within these approved senders lists box.
  8. Click Use existing or create a new one, type in a new list name, and click Create.
  9. Click the list name to use an existing list as your approved sender list.

Add Email Addresses or Domains to the Spam List

If you would like to add email addresses or domains to the spam list, you need to:

  1. Hover over the list name, click Edit, and then click Add.
  2. Enter an email address or domain name.
  3. Click Save.

You can now repeat the steps to add more email addresses or domains to the list.

Note: The above-described options affect the behavior of the Gmail spam filter across the entire organizational unit where the filter is used. The options have a higher priority than local Gmail spam filters, which means that any settings that differ from them will be overridden.

If you use Gmail only for personal emails and don’t have access to G Suite, you can still change how the spam filter Gmail uses to filter malicious emails behaves by going to Filters tab under Gmail spam folder settings and creating new filters.

  1. Log in to your Gmail account
  2. Click the gear icon at the top right and then select Settings.
  3. Go to Filters and blocked addresses and click create a new filter.
Set up your Gmail spam filter
  1. Fill in the required fields.
  2. Click Create filter, check the Never send it to spam and also Apply filter to matching messages boxes, and click Create filter again.

Unfortunately, creating a spam filter for Gmail is not exactly simple, which is why we recommend you use Clean Email instead.

How to Avoid Getting Caught by Gmail Spam Filter

No software is perfect, and that’s especially true when it comes to email spam filters. Despite the numerous improvement Google has implemented over the years, the Gmail spam filter is still far from perfect. Sometimes it misses a dangerous spam email instead of moving it directly to the trash folder, and sometimes it marks legitimate email messages as spam instead of allowing them to reach the inbox.

If you’re email messages are constantly getting caught by the Gmail spam filter, you should familiarize yourself with the main factors that can impact the deliverability of email messages.

Factor 1: Email Content

Do you sometimes read spam emails out of sheer curiosity? If so, you definitely know that they tend to be full of grammar and spelling errors. The Gmail spam filter analyzes email content and flags all emails that don’t seem legitimate, so make sure to proofread your emails before you click the Send button. You should also avoid common spam trigger words, such as credit, cash, reward, income, passwords, and so on. Of course, the presence of a couple of spam trigger words alone isn’t enough to convince the Gmail spam filter that your emails are junk, so there’s no reason to obsessively avoid all of them—that would probably be impossible.

Factor 2: Domain Name

Gmail maintains a list of malicious domain names, which have been blacklisted for sending spam emails. If your email address uses a blacklisted domain name, there’s a very high chance that the Gmail spam filter will automatically mark all emails from it as spam. To check if your domain name is blacklisted, you can use a blacklist checker like MX Lookup, which will check it against over 100 DNS-based email blacklists.

Factor 3: Email Header

Email headers are hidden code snippets in emails that contain information about the sender, the recipient, the email's route to get to the inbox, and various authentication details. In Gmail, it’s possible to view email headers by selecting “More” (three vertical dots) and “Show original” in any open email message. Spammers sometimes edit email headers to hide their true identity or make it seem as if they were somebody else. Email headers can also become corrupted by a buggy or misconfigured email client, so don’t hesitate to switch to a different email client if your emails are getting caught by the Gmail spam filter.

Factor 4: Attachments

Cybercriminals commonly distribute malware via email attachments because they can target thousands of email users without much effort. The good news is that all modern email services analyze attachments and look for malware. The bad news is that the same security mechanisms email services use to protect their users sometimes backfire and categorize legitimate attachments as dangerous. To avoid this problem, consider sharing files as links using cloud storage services.

Factor 5: Get Whitelisted

The only surefire way how to never get caught by the Gmail spam filter is to ask the recipient to whitelist your email address. If you’re a marketer or a business, tell your recipients to add address to their address book. The Gmail spam filter will automatically interpret this as a clear indication that emails from your email address shouldn’t end up in the spam folder.

Use Clean Email in Addition to Gmail Spam Filter

Clean Email is a bulk email organizer that allows you to effortlessly create Gmail spam filter rules without changing your Gmail spam settings. This web-based tool uses intelligent algorithms to separate email messages according to their category. While Gmail spam filter can only tell apart from legitimate messages from spam, Clean Email can recognize subscription emails, social media notifications, unsolicited advertising emails, and much more.

Customize your Gmail spam filter with Clean Email

Clean Email allows you to manage emails in bulk, and you can tell it to apply various actions automatically in the future just by clicking on a single button. For example, you can automatically mark all emails from social media networks as read so they don’t steal your valuable time and bury emails that are actually important. Clean Email records statistics about how many emails were affected by automation rules, so you can see at a glance how it's working.

What’s more, Clean Email can protect you from spam by automatically unsubscribing you from unwanted email subscriptions. The reason why unsubscribing from email subscriptions is such a good idea is simple: cybercriminals like to steal massive email lists from companies that send out newsletters and marketing emails and use the stolen email addresses for spam distributions. Sometimes, the companies themselves sell collected emails to spammers or other companies.

Unsubscribe from spam emails with Clean Email

To get started with Clean Email, all you need to do is sign in with your email address and current password used to access your mailbox. You can sign in with Gmail, Yahoo, Outlook, iCloud, Fastmail, AOL, Office 365, and many other secure email providers.


There are several spam settings Gmail users can tweak to ensure that no spam messages can reach their inbox, but they do have their limitations. Fortunately, there are also third-party solutions like Clean Email. This excellent addition to Gmail spam filter lets you effortlessly create smart automation rules that organize your inbox for you and help you be more productive.

Clean Email Team

Updated on Apr 16, 2021

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