Mozilla Thunderbird 149.0: New Contact Export and EWS Sync Features
On March 24, 2026, Mozilla Thunderbird 149.0 was released—a cross-platform client for email and RSS feeds. Builds are available for Windows, macOS, and Linux via the Release Channel on the official website. This is a standard release, not ESR. For long-term support, use Thunderbird 140.8.1 ESR, which receives updates for a year from its July 2025 release.
Version 149.0 focuses on address book improvements and integration with Exchange Web Services (EWS), plus 24 bug fixes and security patches.
Key Address Book Updates
Address books can now be created directly in the Account Center, simplifying contact management without extra steps. A new feature for exporting selected address book entries lets developers and admins quickly transfer data to other systems or backups.
- Selective contact export: support for exporting chosen items in standard formats.
- Creating address books in Account Center: centralized management without switching sections.
These changes tackle typical tasks for mid/senior specialists setting up corporate email.
EWS Favorite Messages Sync
Favorite messages via the EWS protocol now sync across devices. This is crucial for users working with Exchange servers: "Favorite" labels stick when switching between desktop, laptop, or mobile clients.
The feature leverages Thunderbird's built-in bidirectional sync mechanisms, minimizing delays. Testing confirms stable performance on Outlook/Exchange Online servers without extra plugins.
Example scenario: a user marks an email as favorite on desktop—the label appears on the mobile device within seconds on the next sync.
Security and Fixes
The release includes patches for 24 vulnerabilities, including previously identified issues in protocol handling and message rendering. The update is mandatory for production environments where Thunderbird serves as the primary MUA.
- Critical fixes: vulnerabilities in EWS parsing and address book.
- Other: UI stability and Linux performance improvements.
Immediate update recommended for all installations.
Comparison with ESR Branch
| Characteristic | Thunderbird 149.0 | Thunderbird 140.8.1 ESR |
|------------------------|-----------------------|-------------------------|
| Support Duration | Standard cycle | 1 year from July 2025 |
| New Features | Contact export, EWS sync | Basic security updates |
| Stability | High, with fixes | Maximum for legacy |
ESR is ideal for environments where predictability is critical, but it skips fresh improvements like EWS sync.
Key Takeaways
- Exporting selected address book entries simplifies data migration.
- Syncing favorite EWS messages across devices without plugins.
- Creating address books in Account Center for centralized management.
- 24 security patches: mandatory update for all deployments.
- Not an ESR release: for LTS, use 140.8.1.
— Editorial Team
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