If your spam filter is working correctly, 99% of incoming spam should be automatically flagged and moved to your spam folder. But what if you’re receiving high volumes of spam due to a past data breach or AI-powered spam bots flooding your spam folder? The extra volume of spam makes finding any legitimate emails that were flagged as junk almost impossible.

Setting up custom message rules in Thunderbird can help you find and delete spam messages based on the From name or Subject line and automatically remove them, leaving only a handful of messages for you to review for false positives.

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Notes & Tips

Before creating filters, sort your spam folder by from name or subject to quickly find the junk mail that you receive the most.
You can also add rules to block specific email addresses, although most spam is never sent from the same address more than a few times, so we recommend creating rules based on the From name or Subject lines
If you connect to mail using the older POP3 protocol, these rules will not work. Switch your account to IMAP in order to access the Spam folder in Outlook.

Posted April 15, 2026

Open Thunderbird and select Tools > Message Filters from the top menu.

Select your account from Filters For: list and click the New button to create a new filter.

Give your filter a name (e.g. Delete Repeat Spam). Change Getting New Mail selection from “Filter Before Spam Classification” to “Filter After Spam Classification”. To make the filter run automatically, check the box next to “Periodically, every 10 minutes".

Change “Match all of the following” to “Match any of the following”. To filter mail by the from name, choose From > Contains and enter a keyword phrase. Click the plus button to add additional rules. To filter by Subject, first choose Subject instead of From. Once your filter keywords have been added, choose Delete Message in the Perform these actions section, or move the messages to your trash folder if you still want to be able to access deleted emails. Click OK to save your new filters.

Automatically Delete Repeat Spam in Thunderbird for MacOS

Notes & Tips

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