What is Spamassassin and How Does it Work?

Nov 27, 2023

Our inboxes are constantly bombarded with emails competing for attention. It’s a never-ending stream where important messages often swim alongside unwelcome spam.

Spamassasin - cover photo

But what if you could filter out that digital junk mail with ease?

That’s exactly what Spamassassin promises. It’s the hero of email management, and chances are, it’s working quietly behind the scenes of your inbox right now.

Read on to see how Spamassassin works to keep your inbox clean and your messages spam-free.

What is Spamassassin (by Apache Software Foundation)?

Spamassassin, developed by the Apache Foundation, is an anti-spam tool that email servers use to sort out unwanted emails.



It analyzes each message and assigns a spam score based on various Spamassassin tests like Bayesian filtering, email authentication methods such as DomainKeys Identified Mail, and checks against online databases for sender reputation.

What does Spamassassin do?

✔️ Uses lots of tests to find spam – it checks emails in many ways to catch spam.

✔️ Free to use

✔️ Simple to add new rules – its rules are easy to read and change, so you can keep up with spammers.

✔️ Doesn’t need much setup – you don’t have to keep updating it with your email info.

✔️ Lets you set your own rules – after it finds spam, you can decide what to do with it on your email server or in your email app.

Read why billions of emails will go to spam in 2024.

What happens to your emails? Step-by-step explanation

STEP 1: An email arrives

First, an email comes into the mail server.

STEP 2: Apache Spamassassin starts checking

It begins to examine the email’s details.

STEP 3: Checking the sender

The tool looks at who sent the email. If the sender seems suspicious, the email gets some points added to its spam score.

STEP 4: Looking at the email body

Apache Spamassassin reads the words in the email. If it finds words that spammers often use, it adds more points to the email’s spam score.

STEP 5: Adding up points

Each issue found in the email adds points to its spam score. The more points, the more likely it is spam.

STEP 6: Deciding if it’s spam

After all the checks, if the email’s Spamassassin score is high, the tool labels it as spam.

STEP 7: What happens next

If the email is spam, it might go to a spam folder or get a warning. If the Spamassassin score is low, it goes to the inbox.

STEP 8: Configure Spamassassin

You can adjust how the tool works. It’s easy to configure and add new rules.

Who uses Apache Spamassassin?

Here is the list of organizations and people for whom Spamassassin might be particularly important. 👇

  • Email service providers (ESPs) use Spamassassin to filter incoming mail for their users. It keeps spam out of inboxes with bulk email checks.
  • Companies of all sizes leverage Spamassassin to protect their employees from spam and to make sure that their outgoing emails are not marked as spam.
  • System administrators who manage email servers implement Spamassassin to reduce the amount of spam on their networks.
  • Web hosting service providers often include Spamassassin as part of their email service offerings to clients, ensuring only legitimate emails come through.
  • Individuals running their own mail servers may rely on SpamAssassin to filter their personal email.
  • Developers and IT Professionals integrate spam filtering into custom applications or email solutions they are developing or managing.

What is the Spamassassin score?

The Spamassassin score is a number that helps identify spam. It shows how likely an email is to be considered as such.

Each email processed by Spamassassin goes through a series of tests, and each test either adds or subtracts from the email’s overall score. The tests examine the email’s content and formatting, as well as the sender’s reputation and the email authentication protocols used.

If an email does not pass authentication checks such as DomainKeys Identified Mail (DKIM), it might get a higher spam score. When the content of the email contains phrases commonly found in spam emails, that will also increase the score.

The spam score may be lowered if the email comes from a trusted sender or includes elements that are typical of legitimate correspondence.

What score is good for email providers?

🟢 A good SpamAssassin score is anything below 5.0.

Then an email is unlikely to be filtered into the spam folder. This means you’re sending non-spam messages and you’re one of the legitimate senders.

🔴 Scores above 5.0 signal that an email is more likely to be considered spam and may not reach the inbox.

Email senders try to achieve a very low Spamassassin score for each email message. The goal is to get their emails delivered. Individual users or email administrators can configure the threshold score to be more or less strict based on their preferences.

Poor Spamassasin score: how to avoid it

Nobody wants to be marked as spam in people’s email inboxes. We’ve got a bunch of tips, so you can avoid that in front of your email client.

#1 Validate your email lists

Validating your email list = cleaning it up and making sure your email score is spotless.

You remove any addresses that bounce or are no longer in use because the mail message will not reach them. It’s a good practice because sending emails to a bunch of non-existent or unengaged recipients is a red flag for spam filters. You don’t have to delete them – you can put them in a separate folder if you find it hard to say goodbye. However, your default score will certainly go up and most mailbox providers will ramp up your results.

👉🏻 To do that, use Bouncer, an email validation tool. It’s very accurate (99,5% accuracy rate), so you know your emails will go to the right people.

Bouncer website

🟠 It’s fast
– it can check a lot of emails in an hour, so you don’t have to wait long. It provides email insights within just a few minutes for smaller lists.

🟠 Easy to use – customers say it’s simple and the reports are effective for individual emails as well as bulk lists.

🟠 Great help when needed – if you have questions, their team is there to assist you.

🟠 Has many features – it can guess how many emails might bounce back and spot bad emails that could cause trouble. All thanks to the Deliverability Kit, Toxicity Check, Email Verification, and more.

🟠 Keeps your info safe – it follows strict rules to protect your data like all high-quality mail programs.

🟠 Price is fair – you pay for what you use, and it’s not affordable compared to competing products.

🟠 Try it for free – you can test checking up to 10,000 emails before deciding if you want to use it more.

#2 Show clear from and reply-to fields

Once they’re clear, people know who you are and where to respond. You show that you’re not sending spam.

The from field indicates who is sending the email. It usually displays the sender’s name and email address. This field helps recipients immediately identify who the email is from.

For example: Anne Smith [email protected]

It shows that Anne Smith is sending the email and provides her email address.

The reply-to field is used to specify where responses to the email should be sent. This can be different from the from address.

For example: Customer Support [email protected]

If the recipient hits reply, their response will be sent to the customer support team instead of Anne Smith’s personal email.

Spam filters, like Spamassassin, often look at these fields to decide if an email is unwanted and that the probability of spam is high. If these fields are clear, your emails are more likely to end up in the inbox, not the spam folder.

👉🏻 Always check these fields before sending your emails to keep your spam score low and your messages welcomed by your readers.

#3 Do not purchase or rent email lists

Buying or renting email lists can hurt your email campaigns. When you use such lists, you send messages to people who didn’t choose to hear from you. Most often, the emails are marked as spam.

Spamassassin notices it and may give you a high spam score.

If your score gets too high, even your good emails might not reach people’s inboxes.

👉🏻 It’s best to grow your list naturally with people who really want to get your emails.

#4 Check your emails for HTML errors

Mistakes in the code can make your emails look like unwanted messages. And it’s not something you strive for, right?

A clean and error-free HTML is a sign of a professional email, and it helps mail servers trust your content. If your HTML has errors, the Spamassassin program might think your email is spam and block it.

👉🏻 Before you send an email, test it and fix any HTML issues.

#5 Set up authentication

Authentication is a digital signature to prove your emails come from a trusted source. If emails are properly authenticated, it tells email services that your messages are legitimate and not spam.

It can reduce your spam level because it’s harder for spammers to fake this kind of proof.

👉🏻 Double-check if your email system has SPF, DKIM, and DMARC set up. It alerts Spamassassin and other spam filters that you’re sending proper emails that eventually land where they’re planned to.

#6 Avoid too many images to prevent landing in a spam folder

If an email has too many images, it might be given a negative value by spam filters, which can hurt an email marketer’s positive reputation.

Spamassassin can automatically filter out emails that have lots of images and not much text because spammers often use images to hide words they don’t want filters to see.

👉🏻 Use a good balance of text and images in your emails.

#7 Don’t use spam trigger words

These are words that often cause negative scores from spam filters when they evaluate emails. Trigger words can be in the message body, the email headers, or even in the alt text of images – so you need to check them all.

Spam filters scan these areas to decide if an email might be spam. If you use too many words that are known for being in spam, your emails could end up in the spam folder instead of the inbox.

Here are a handful of trigger words examples:

  • free
  • guarantee
  • no obligation
  • risk-free
  • urgent
  • winner
  • limited time offer
  • make money
  • miracle
  • exclusive deal
  • cancel at any time
  • congratulations

👉🏻 Choose your words carefully to make sure your emails look professional and trustworthy.

Bouncer CTA

Conclusion on Apache Spamassasin

Let’s close with a nod to Spamsssassin, the tool that keeps annoying spam out and lets the good emails in.

And while Spamassassin filters out spam emails, Bouncer keeps your email list in tip-top shape. No more scrolling through endless spam — just the emails you actually need to see.

Give Bouncer a try! Sign up and validate 10,000 emails for free.

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