5 best anti-spam email filters for Thunderbird

by Tashreef Shareef
Tashreef Shareef
Tashreef Shareef
Windows & Software Expert
Tashreef Shareef is a software developer turned tech writer. He discovered his interest in technology after reading a tech magazine accidentally. Now he writes about everything tech from... read more
Affiliate Disclosure
  • In this article we consider the best spam filters for Thunderbird to help you keep the junk where it belongs.
  • We provide you with an effective spam filter that protects you against malware by filtering spam from genuine emails.
  • Below you can find a program that works on both desktop computers and mobile devices.
  • We also give you a built-in spam filter solution in case you don't want to use third-party software.
Best anti-spam email filters

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Thunderbird is the best free email client for Windows allowing the users to manage multiple email accounts with ease. It also offers offline access to emails a feature missing from the built-in Windows mail app.

Thunderbird supports third-party calendar app integration for event and appointment reminders. And for the features that are not available by default, the huge collection of third-party add-ons make up for it.

Any reliable email client includes an efficient spam filter, and the Thunderbird is no exception. This open source email client also comes with a highly-efficient built-in spam filter that uses Bayesian statistical analysis to determine spam from legit emails.

Although built-in spam filter takes some time to learn about the incoming emails, it starts working efficiently once the learning process is over.  However, for some the built-in spam filter might be inefficient mainly due to the fact it takes its own time to learn about the incoming emails before start putting them in the spam box.

Fortunately, there are a couple of third-party spam filter add-ons available for Thunderbird offering free junk classification features, so read on for more details.

Best email spam filters for Thunderbird


SpamFighter Spam Filter for Thunderbird

SPAMFighter is a third-party spam filter that works with Thunderbird, Microsoft Outlook, Outlook Express, Windows Mail and Windows Live Mail. It comes in two versions Stand and Pro.

Irrespective of the version, SPAMFighter is a highly-efficient spam filter that can protect the users against malware, virus and phishing attacks filtering spam from genuine emails.

SPAMFighter works in real time scanning every incoming mail and moves the email based on the result to either your Inbox or spam folder. The Spam Blocker feature allows you to tag any undetected email as spam.

The developers have offered multi-language users interface. The Blacklist feature makes it easier to block emails based on email IDs and domains and it also comes with an automatic whitelist management feature.

The Pro version of SPAMFighter costs $29 and offers an additional set of features. The Pro users can protect multiple email IDs, license to use in a company, filter emails based on languages, unlimited Black and Whitelist entries and no SPAMFighter footer in your emails.

SPAMFighter for Thunderbird is one of the highly rated spam filters that can help you keep the spam out of your inbox. While the free version may have some limitations, the Pro version is well worth the investment considering the features on offer.

    Get SPAMFighter


MailWasher Best Anti Spam Filter for Thunderbird

MailWasher is a free anti-spam filter that works with all the major email clients including Thunderbird, Outlook Express, Windows Live Mail and Hotmail. MailWasher comes in both free and Pro version with a few differences which I will talk later in the article.

It is an effective spam filter that works on both desktop computers and mobile devices. It also lets you preview all the incoming emails before forwarding it to your Thunderbird inbox.

You can choose to read the emails on the server and download it to Thunderbird inbox or delete the unwanted / spam emails before it reaches your inbox. One advantage of this feature is that it allows you to destroy any incoming emails with malware and virus from reaching your computer.

MailWasher uses the Bayesian statistical analysis technique to determine the nature of incoming mail based on the sender and the email messages. It comes with a comprehensive spam filter tools including White and Blacklist, customizable filters and external blacklist option.

The Pro version of MailWasher costs $40 and allows you to use multiple email addresses, offers to recycle bin for deleted emails, full preview pane for email, the ability to sync with Mailwasher mobile apps and technical support from the developers.

The lack of country code based spam filtering or blocking feature is something we missed on an otherwise excellent spam filter.

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Get MailWasher for Thunderbird

Thunderbird’s Built-in Spam Filter

Thunderbird Spam Filter Enabled

Thunderbird comes with a built-in Spam filter as we discussed in the article earlier. If you don’t want to use a third-party Spam filter, it is right time to give the built-in spam filter a fair shot.

The upside to the built-in spam filter in Thunderbird is its ability to filter spam messages from legitimate emails accurately. But, for that to happen the user must train the Thunderbird to identify junk mail by using the Junk tool button to mark a message as junk or not. After some time, Thunderbird will automatically classify spam mail and put it in the spam box.

Thunderbird uses external classifiers like SpamAssassin, bogofilter, DSPAM and POPFile to identify spam emails. The user can also exclude emails from the personal address book and collected addresses from being marked as spam.

For Thunderbird spam filter to work, make sure you enable the adaptive junk mail control from the settings. Here is how to do it.

  1. Launch Thunderbird and click the Menu icon.
  2. Go to Options > Account Settings.
    Thunderbird Email Client Meu Options Account Setting
  3. Click on Junk Settings tab. Check “Enable adaptive junk mail control for this account” option.
    Thunderbird Spam Filter Enabled
  4. Check “Trust junk mail headers set by [your preferred classifier]” option. (optional)
  5. Click OK to save the changes.

Additional Thunderbird spam filters

There are a few other spam filters available for Windows that can also be used with Thunderbird, but we have listed them separately because most of these filters haven’t received any update in the last few years or simply don’t offer free spam filter version except 30 days trial.



CleanMail is an anti-spam and Anti-virus filter that works with Thunderbird and other email clients. The programs can protect you from not only spam but also from malware and phishing attacks. It uses SpamAssassin classifier combined with Bayes database to determine spam from other emails.

Other notable features by CleanMail include anti-virus filter, attachment filter, DNS Blacklist, Shared Fingerprint filter and delay filter. The Cleanmail plan starts at $279 for 10 email addresses but you can try the tool using a 30-days free trial.

Get CleanMail free trial



POPFile is an automatic email classification program that filters spam emails coming to your email address. POPFile uses categories for classification but also allows users to create their own categories like work and personal category for better email management.</p>

The software uses Bayes algorithm and requires the users to train the tool by classifying spam and Non-spam mails manually before it can effectively start classifying spam automatically. You can download the latest version of POPFile from the official website which was last updated in September 2015.

Get  POPFile

You can read about more spam filters in our detailed article on the best Windows email spam filter most of which are also compatible with Thunderbird and Windows email clients.

JunQuilla – Use this add-on for better spam management


JunQuilla is not a spam filter but an add-on for Thunderbird that shows information about the spam management process. JunQuilla shows a percentage match column from 0-100 determining which email is complete spam and which one needs a re-look so that you don’t miss out on important emails because the spam filter classified it as otherwise.

Get JunQuilla for Thunderbird 


In this age where email scrapping tools help the promoters bombard anyone with their sales pitch through spamming, it is important to have one of these best anti-spam filters for Thunderbird protecting your interest.

If you use email accounts from Hotmail or Gmail, you don’t need spam filters as these services offer their own spam filters. However, for anyone using a custom email address with Thunderbird needs to have one of these spam filters to keep their inbox clean.

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