thunderbird@esr

Install command: 
brew install --cask thunderbird@esr

Names: Mozilla Thunderbird ESR, Mozilla Thunderbird Extended Support Release

Customizable email client

https://www.thunderbird.net/en-US/download/esr/

Development: Pull requests

Cask JSON API: /api/cask/thunderbird@esr.json

Cask code: thunderbird@esr.rb on GitHub

Current version: 140.10.0esr

Requirements: macOS >=

Conflicts with casks:

thunderbird 150.0 Customizable email client Mozilla Thunderbird

Analytics:

Installs (30 days)
thunderbird@esr 44
Installs (90 days)
thunderbird@esr 116
Installs (365 days)
thunderbird@esr 434