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Thunderbird Sieve Extension

Sieve is a powerful script language for server-side mail filtering. It is intended to be used with IMAP and thus it is widely spread. Many IMAP Server are capable of running sieve filters. Sieve stores and runs all script on the server-side.

Now there is the dilemma - you have access to a server supporting sieve but, how do you manage your scripts on this server?

You can use telnet for this purpose, but that is far to uncomfortable, not applicable for a normal user and almost impossible with secure connections. Wouldn't it be great to activate, edit, delete and add sieve scripts with a convenient interface? That is exactly what the Sieve Extension offers...



The extension is an implementation of the sieve management protocol (RFC 5804). Currently only "SASL Plain", "SASL Login", "SASL CRAM MD5", "SASL SCRAM SHA1" and "SASL SCRAM SHA256" Authentication mechanisms are supported, others may be implemented on request.

The graphical script editor supports the Sieve Filter Language (RFC 5228).

The project exists since 2006 and can be considered as stable. Statistics are available at ohloh

It is translated into French, Spanish, Russian and German. If you're interested in translating or localizing the extension into your language, just sign up at crowdin and start translating (Crowdin is a free collaborative translation tool). If you added a translation please drop a note via email or open a ticket, so that I can regenerate the localised files.

For more details on contributing refer to the Contributing Guidelines

A big thank you to every one who have contributed and supported this project.

If you want to support this project consider donating

  • Code, patches or localisations

  • via Paypal PayPayl donate button

  • via Bitcoin 1GEnrRVobFYuqYj2opdvRQNtG3Z8znvfKw

Questions and Bugs

The best for questions is the public mailing list at!forum/sieve-app or via mail . But you can also send a private mail to schmid-thomas at

Concerning bugs please use the issue tracker or send a private email to schmid-thomas at . You find more details on reporting bugs in the Contributing Guidelines

Give me 1-2 weeks time for a reply. If you did not receive a reply at all, it might be a good idea to check your spam filter.


The extension is free and open source software, it is made available to you under the terms of the GNU Affero General Public License (AGPLv3).

Refer to Licensing information for details.


You are looking for the most recent release?

Just go to the releases page and download the latest stable xpi or view the release notes.

Firefox user have to do a right click on the XPI download and select "Save link as" otherwise Firefox will steal the link and try to install the addon it into Firefox which will fail

The addon is restartless, so there is no need to restart Thunderbird upon installation and deinstallation.

Sometimes Thunderbird fails to invalidate its cache when updating a restartless addon. The result is the new version is displayed in the addons dialog but the old cached code is still be used. In such a case uninstall the addon, then restart thunderbird, restart it again and finally install it again. This ensures the cache gets correctly invalidated.

Developments Builds

You are looking for the latest "bleeding edge" features and willing to risk more instability? Or you might even want to test out newly added code to help identify and debug problems?

You can find the development builds also in the release section. They are marked as prerelease. They will update to newer releases but not to newer prereleases.