At Mozilla, localization refers to adapting the user interface and messages to different cultural and regional needs. Localization is a broader term than translation because it involves extensive research into the target culture, and in result touches not only text and UI translation but also cultural adaptation of icons, communication styles, colors, and UX.

Questions about Thunderbird localization should be directed to the Localization Coordinator. Contact information is on the Thunderbird Project page in Pontoon.