Definition

💡 A spam filter is a feature in email services whose purpose is to automatically detect and block unsolicited, unwanted, and potentially harmful messages from reaching your inbox. An effective spam filter can significantly reduce the need for manual inbox organization, and it can also protect you from phishing attacks and other mail-based cyber threats.

What does an email spam filter do?

An email spam filter scans and assesses every incoming message against a set of criteria to determine the likelihood of it being spam. These criteria can include the sender's address, the email's content (e.g., certain keywords or phrases), the email's metadata, and the reputation of the sender's IP address.

If the filter deems an email to be spam, it will typically move it to a dedicated "Spam" or "Junk" folder, where the user can review it if they wish. If configured to do so, the filter may delete the message entirely. Only messages not deemed to be spam are allowed to reach the inbox.

Example

The work of a well-configured spam filter is largely invisible. Without it, your inbox would be full of messages with subject lines like:

"You've won a lottery!"
"Claim your $1,000,000 reward now!"
"URGENT: Your account has been compromised!"
"Buy cheap pharmaceuticals online!"
"Meet your perfect match on our dating site!"

These are all examples of common spam emails that a well-configured spam filter would automatically detect and handle appropriately, saving the user from the hassle of manually deleting them and protecting them from potential scams or threats.

How to set up a spam filter

Most mail services come with built-in spam filters that are enabled by default. These filters are continuously updated and improved by service providers to ensure they can effectively detect and block spam.

Users can further enhance the performance of these spam filters by "training" them. This involves manually marking spam emails that the filter missed as "Spam" or "Junk," and vice versa for legitimate emails that were incorrectly marked. Over time, the filter will learn from these actions and become more accurate.

How to turn off a spam filter

Most major email services, including Gmail, Outlook, and Yahoo, don't provide an option to completely turn off their spam filters. This restriction is in place to protect users from potentially harmful or malicious emails that could compromise their security or clutter their inboxes.

However, there is a workaround to bypass the spam filter by creating a message filter that ensures certain emails are never marked as spam. For example, in Gmail, you can set up a custom filter to prevent incoming emails from being sent to the Spam folder:

Open Gmail and go to Settings.
Navigate to the Filters and Blocked Addresses tab.
Click on Create a new filter.

In the filter criteria, type a random, unique string of characters in the DOESN'T HAVE box, such as "fhq28903r0afhngljsds."
Click Create filter and then select Never send it to Spam.