Thunderbird Beta for Testers

Jun 24, 2026

Thunderbird version 21.0b1

Changed:
- Animation setting now allows On, Off, and System Default options
- Modernized 'Fetching mail' account settings screen

Fixed:
- Modernized 'Composition defaults' screen
- Application could crash due to memory exhaustion
- Application could crash when rendering long messages
- Inline images were shown as attachments instead of displaying in message
- Server search results could disappear
- Links failed when trailing punctuation incorrectly included in URLs