SolidAssist for Thunderbird

Write better emails, faster, without leaving Thunderbird.

SolidAssist brings AI-assisted email drafting and summarization directly into your Thunderbird workflow. Select an email, choose an action, and review the result before anything is sent.

What you can do

Generate editable reply drafts for the selected email
Summarize long messages in seconds
Refine drafts with your own instructions
Use connected knowledge sources for more relevant answers
Review the sources used to produce a response
Send approved replies using your connected email account

Designed for your workflow

Open SolidAssist from the top toolbar
Use direct actions from message menus and right-click menus
Work in a resizable window alongside Thunderbird
Open the complete SolidAssist app in its own Thunderbird tab
Configure keyboard shortcuts and access preferences, knowledge, email accounts, privacy, and security settings

You stay in control

SolidAssist processes an email only after you choose an AI action. Generated drafts remain editable and are never sent automatically. The extension does not request or store your IMAP password.

A SolidAssist account is required. The email account used in Thunderbird must also be connected to SolidAssist so the service can securely identify and process the selected message.

Need help?

The built-in Help Center provides guidance for setup, email connections, AI features, knowledge sources, privacy, and troubleshooting.

Learn more at solidassist.de.

Getting started

Sign in to your SolidAssist account.
Connect the same email account you use in Thunderbird.
Select an email and open SolidAssist from the toolbar, message menu, or right-click menu.

Compatibility

SolidAssist for Thunderbird is designed for desktop versions of Thunderbird. Mobile versions are not currently supported.

Support

For setup guidance and troubleshooting, use the Help Center included with the extension or visit solidassist.de.

SolidAssist for Thunderbird Add-on Privacy Policy

Effective date: November 6, 2026

1. Scope

This Privacy Policy applies specifically to the SolidAssist for Thunderbird add-on. It supplements the general SolidAssist Privacy Policy available at:

https://solidassist.de/apps/solidassist-email/privacy

SolidAssist is responsible for the operation of this add-on and the related SolidAssist service. Privacy questions can be sent to info@solidassist.de.

2. Data accessed inside Thunderbird

To identify the email selected by the user, the add-on accesses:

• The configured email account address and account name
• The selected folder name and folder path
• The selected message identifier
• Message headers required to identify the message
• The message subject, sender, recipients, and date for local display and account matching

The add-on reads the selected message locally to obtain the Message-ID header. It does not upload the email body or attachments stored in Thunderbird.

The add-on does not access or collect the IMAP or SMTP password stored in Thunderbird.

3. Data transmitted to SolidAssist

After the user accepts the add-on data-use notice and explicitly requests an action, the add-on may transmit the following information to https://app.solidassist.de:

• The email address of the selected Thunderbird account
• The selected folder name
• The server-side message identifier required to locate the matching message
• The user’s refinement instructions
• The current generated draft and refinement history
• The final edited reply when the user chooses to send it
• The authenticated SolidAssist session information required to authorize the request

The add-on uses this information only to locate the corresponding message in the mailbox that the user has separately connected to SolidAssist, generate a draft or summary, refine a draft, display relevant knowledge sources, or send an approved reply.

SolidAssist retrieves the full message content from the mailbox that the user has separately connected to the SolidAssist service. The Thunderbird add-on does not upload the message body or attachments from the user’s device.

4. Authentication and mailbox credentials

The add-on uses the user’s existing authenticated SolidAssist session. It does not collect, display, store, or transmit the IMAP or SMTP credentials saved in Thunderbird.

Mailbox credentials entered separately into SolidAssist are handled by the SolidAssist service under the general SolidAssist Privacy Policy. The add-on does not have access to those credentials.

The add-on does not create advertising or tracking cookies. An essential SolidAssist authentication cookie may be used to keep the user signed in and authorize requests.

5. AI processing and knowledge sources

The selected message content is processed according to the AI service mode selected in the user’s SolidAssist settings.

The Standard processing option operates on SolidAssist-managed infrastructure and does not send email content to an external cloud AI provider.

The Fast processing option may use an external cloud AI provider. Fast can be enabled only after the user opens the SolidAssist Privacy settings, reviews the currently configured provider or providers, reviews what information will be transmitted and for what purpose, and provides explicit consent.

The currently configured cloud provider information and the associated data-use explanation remain available in the SolidAssist Privacy settings.

The user can revoke cloud-processing permission at any time from the SolidAssist Privacy settings. Revoking permission immediately prevents further use of external cloud AI processing. The user can continue using the Standard processing option.

If the configured cloud provider or required consent changes, SolidAssist may require the user to review the updated information and provide consent again before Fast processing becomes available.

The Thunderbird add-on does not independently select, activate, or change a cloud AI provider or the user’s cloud-processing consent.

6. Local storage

The add-on stores only the following information locally in Thunderbird:

• The user’s acceptance of the add-on data-use notice
• Extension interface preferences
• The preferred size and position of the standalone assistant window
• Temporary navigation information used to open the requested SolidAssist settings page

The add-on does not permanently store email bodies, attachments, generated drafts, summaries, or refinement instructions in Thunderbird extension storage.

Removing the add-on removes its locally stored extension data. Removing the add-on does not automatically delete the user’s separate SolidAssist account or data.

7. SolidAssist service storage

SolidAssist may temporarily store generated drafts, summaries, source references, and related processing results in encrypted server-side caches to provide the service efficiently. These encrypted cache entries expire automatically and are retained for no longer than 30 days.

SolidAssist may also retain account identifiers, action type, processing status, timestamps, and credit or service usage records for account security, service operation, and usage reporting.

Emails sent by the user may remain in the connected mailbox according to the mailbox provider’s normal storage and retention settings.

Additional retention and account-deletion information is provided in the general SolidAssist Privacy Policy.

8. Sharing and sale of data

The add-on does not sell personal data.

The add-on does not use email information for advertising, profiling, or unrelated analytics.

Data is transmitted to SolidAssist and to service providers required to operate the SolidAssist service.

When the user explicitly enables Fast processing, relevant email content, user instructions, draft text, and relevant knowledge excerpts may be transmitted to the external cloud AI provider or providers currently identified in the SolidAssist Privacy settings.

External cloud AI processing occurs only while the user’s permission remains active. The user can review or revoke this permission at any time in the SolidAssist Privacy settings.

The current provider information, processing purpose, and applicable data-use details are available in SolidAssist and in the general SolidAssist Privacy Policy:

https://solidassist.de/apps/solidassist-email/privacy

9. User choice and control

The add-on displays a data-use notice after installation. Email-related requests are disabled until the user accepts this notice.

The user can decline the data transmission and remove the add-on.

The user controls when an email is summarized, when a draft is generated or refined, and when a reply is sent. The add-on does not process or send email content automatically in the background.

Users can disconnect a mailbox, manage AI and privacy preferences, or delete their SolidAssist account through SolidAssist.

10. Security

All communication between the add-on and SolidAssist uses encrypted HTTPS connections.

The add-on requests only the Thunderbird permissions required to identify the selected message, access configured account information, display its interface, and communicate with SolidAssist.

11. Changes and contact

This policy may be updated when the add-on’s functionality or data handling changes. Material changes will be disclosed through an updated policy and, where required, a new consent request.

For privacy questions or requests, contact:

info@solidassist.de
https://solidassist.de/#contact

Some add-ons ask for permission to perform certain functions (example: a tab management add-on will ask permission to access your browser’s tab system).

Since you’re in control of your Thunderbird, the choice to grant or deny these requests is yours. Accepting permissions does not inherently compromise your browser’s performance or security, but in some rare cases risk may be involved.

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SolidAssist for Thunderbird 1.0.0

by SolidAssist

About this Add-on

Developer’s Comments

Version Information

Version 1.0.0 Released نومبر 6, 2026 82.9 KiB Works with Thunderbird 140.0 and later