HOW TO: Change Language in SquirrelMail

Extract the package's three directories (help, images and locale) to your SquirrelMail installation directory.

Edit /config/config.php -- somewhere near line 849 you will need to change:
$squirrelmail_default_language = 'en_US';

Language Name, Language Code, Country Code
------------- ------------- ------------
Chinese (Traditional), zh, CN
Chinese (Simplified), zh, TW
Danish, da, DK
Dutch, nl, NL
French, fr, FR
German, de, DE
Italian, it, IT
Japanese, ja, JP
Korean, ko, KR
Portuguese, pt, BR
Spanish, es, ES
Swedish, sv, SE