Install sylpheed-i18n by entering the following commands in the terminal:
sudo apt update sudo apt install sylpheed-i18n
Description:
Locale data for Sylpheed (i18n support)
This package provides support for non-English interfaces in the Sylpheed mail client. Current supported locales are: be (Belarusian) bg (Bulgarian) cs (Czech) da (Danish) de (German) el (Greek) es (Spanish) et (Estonian) eu (Basque) fi (Finnish) fr (French) gl (Galician) hr (Croatian) hu (Hungarian) it (Italian) ja (Japanese) ko (Korean) lt (Lithuanian) nl (Dutch) pl (Polish) pt_BR (Brazilian Portuguese) ro (Romanian) ru (Russian) sk (Slovak) sl (Slovenian) sr (Serbian) sv (Swedish) tr (Turkish) uk (Ukrainian) vi (Vietnamese) zh_CN (Chinese) zh_TW (Taiwanese)
Homepage: http://sylpheed.sraoss.jp/en/
Version: 3.5.1-1ubuntu3
Section: universe/mail