Email filtering services keep your inbox safe and legitimate by finding and removing spam messages before you do. However, some spam still makes it through, while others never make it to your spam folder at all.
So, how does email spam filtering work? And is it something you need to think about?
We’ve got you covered.
Below, we’ll walk you through everything you need to know about email filtering software and services to help you prevent spam and protect your customers.
From traditional spam filters that scrutinize content and sender reputation to advanced email authentication services like Valimail, we’ll explain how technology is evolving to make the inbox (and your communications) more secure.
| Key Highlights – Email filters are essential for blocking spam, phishing, and malware, but they aren’t perfect. False positives still happen, especially with important transactional emails. – Not all filters are created equal. The best solutions combine content analysis, reputation checks, and user-level controls to protect inboxes without disrupting business. – Valimail strengthens filtering by authenticating sender identity with SPF, DKIM, and DMARC, reducing false positives and stopping phishing at the source. |
What is email filtering?
Email filtering automatically processes incoming emails to sort, block, or redirect them based on specified criteria. Its primary purpose is to ensure users receive only relevant and safe emails, and it accomplishes this in three ways:
- Segregating spam from legitimate emails
- Protecting users from malicious content
- Organizing emails based on user-defined rules or priorities
Types of email filters
Inbox service providers filter emails through various tools and processes. Here are a few of the most common types of email filters:
- Content-Based Filters: These filters examine the content within the email body and subject line for known spam signatures or suspicious phrases. They analyze attachments for malware or unwanted content and provide a comprehensive check of the email’s contents.
- Header-Based Filters: These focus on the email’s header information by looking at the sender’s domain, the path the email took, and any discrepancies that might indicate spoofing or phishing attempts.
- Blocklist Filters: Blocklist filters automatically reject emails from databases known to send emails to spam domains and IP addresses. Allowlist filters ensure emails from trusted senders bypass the spam filter entirely.
- Bayesian Filters: Bayesian filters adapt over time by learning from user behavior, improving their ability to distinguish between spam and legitimate emails based on the user’s email usage patterns.
- Heuristic Filters: Heuristic filters score emails based on various factors, such as the presence of certain words or the frequency of specific characters. Emails that score above a certain threshold are flagged as potential spam—the others make it to the inbox.
How email filtering works
Email filtering involves several stages designed to scrutinize emails for characteristics typical of spam or malicious content.
Initially, the filter examines an email’s metadata: the sender’s address, the message’s header, and the route it took across the web. It then analyzes the content of the email, looking for known phishing phrases, suspicious links, or patterns associated with spam.
Advanced filters employ machine learning algorithms to adapt to new threats. They learn from the patterns of emails marked as spam to improve their accuracy over time. Once the filter flags an email, it can be blocked, quarantined for further review, or marked and delivered with a warning to the recipient.
Why email spam filtering is important
Email spam filtering isn’t just about cleaning up your inbox (though it helps with that, too). It’s about making email a safe communication space for businesses and consumers.
Here are just a few of the reasons email filtering is essential in today’s inboxes:
- Security: Spam filtering is a critical defense against phishing attempts, malware, and other email-borne threats. Spam filters block malicious emails before they even reach the inbox, reducing the risk of security breaches.
- Productivity: Spam emails can overwhelm inboxes, burying important messages under a pile of irrelevant content. Filtering out these distractions allows individuals and employees to focus on authentic communications.
- Bandwidth: Spam emails consume network bandwidth, mainly when they include large attachments. Filtering spam helps conserve bandwidth for business operations and ensures faster access to legitimate emails.
- Data Protection: Many spam emails aim to phish for sensitive information. Effective spam filtering protects users from inadvertently disclosing confidential data, safeguarding personal and corporate information from exploitation.
- Compliance with Regulations: Certain industries are subject to strict data protection and privacy regulations. Spam filters help organizations comply with these legal requirements, avoiding potential fines and legal issues.
- IT Support Tasks: With fewer spam emails reaching users, IT departments receive fewer help desk calls related to spam and malware infections. This allows IT professionals to focus on more strategic tasks and projects.
- User Experience: Spam-free inboxes contribute to a cleaner, more organized email environment, improving the overall user experience. Users can trust that the emails they receive are relevant and safe.
Essential features of the best email spam filters
While inbox service providers have built-in spam filters, they don’t always provide the comprehensive protection you and your employees need. That’s when a third-party email spam filter service comes in handy.
However, these tools come in all shapes and sizes, meaning every solution isn’t going to be the right fit for your business. Simple spam filters might sift out easy-to-spot threats, while more advanced solutions provide warning tags and one-click report buttons.
Here are the basic criteria to consider when evaluating email spam filters:
- Accuracy: The primary measure of a spam filter’s effectiveness is its accuracy—its ability to distinguish between legitimate emails and spam. High accuracy ensures that spam is reliably caught while minimizing false positives (where legitimate emails are mistakenly classified as spam).
- Integration: An effective spam filter should seamlessly integrate with your existing email infrastructure. Whether using on-premise email servers or cloud-based services, the filter should be compatible with your setup and not require extensive modifications to your existing systems.
- Ease of Use: Spam filtering solutions should have intuitive user interfaces to empower users and administrators to easily manage settings, review quarantined emails, and adjust policies without extensive technical knowledge.
- Scalability: The solution should handle increased email volumes and user accounts without significantly impacting performance or accuracy.
Beyond the fundamentals, you’ll also want to look for features like the following:
- Quarantine Zones: Quarantine zones allow suspicious emails to be held in a safe area for further review. This prevents potentially harmful emails from reaching users’ inboxes while avoiding outright deleting emails that may be false positives.
- Reporting Tools: Comprehensive reporting tools offer insights into the types and volumes of threats being blocked and trends in email traffic. These reports can inform security policy adjustments and provide evidence of compliance with regulatory requirements.
- User Controls: Effective spam filters offer granular controls that allow users to customize filtering rules based on their specific needs. This includes the ability to allowlist trusted senders, blocklist known spam sources, and adjust sensitivity settings.
Top email filtering software and services
Different email filtering services cater to different needs. Some primarily focus on small businesses, while others prioritize enterprises. Each brings a unique approach (and cost) to safeguarding the email channel. However, the best email spam filter solutions typically offer a blend of advanced technologies, such as machine learning, artificial intelligence, and user customization.
Standalone software vs. integrated email filtering services
Standalone software typically refers to on-premise solutions installed and managed directly on an organization’s infrastructure. These solutions offer a high degree of control and customization, allowing you to tailor the email filtering process to your needs.
Integrated email filtering services are cloud-based solutions that provide spam and threat protection as a service. These services are managed externally by the provider and seamlessly integrate with an organization’s existing email systems.
Standalone software
- Pros:
- Highly customizable, allowing organizations to tailor the filtering rules and settings to their needs.
- Often offers a one-time purchase option, potentially reducing long-term costs for businesses.
- Can be hosted on-premise, offering companies complete control over their data.
- Cons:
- Requires in-house expertise for installation, configuration, and maintenance.
- May not be as quick to update with new features or threat intelligence compared to cloud-based services.
Integrated email filtering services
- Pros:
- Cloud-based services offer ease of deployment and scalability, adapting to the changing needs of the business.
- Continuously updated with the latest threat intelligence and features without needing manual intervention.
- Often includes access to expert support and managed services, reducing the burden on in-house IT staff.
- Cons:
- Subscription-based pricing models can become costly over time.
- Some businesses may have concerns about data sovereignty and privacy with cloud-hosted solutions.
Avoid spam filters and false positives with Valimail
Spam filters play a vital role in keeping inboxes clean, but they don’t catch everything, and worse, they sometimes block legitimate emails. That’s a serious problem for critical communications like password resets, alerts, and receipts.
Fortunately, we can help.
Valimail goes beyond filtering by verifying sender identity at the source. Our solutions use SPF (Sender Policy Framework), DKIM (DomainKeys Identified Mail), and DMARC (Domain-based Message Authentication, Reporting, and Conformance) to make sure only authorized senders can use your domain so your real messages land in the inbox, and fake ones don’t.
With Valimail’s automated solution, you can reduce false positives, stop phishing before it hits the inbox, and protect your brand and customers.
Start for free with Valimail Monitor to identify unauthorized senders, find gaps in your authentication, and take the first step toward enforcement.
