Hi, I contacted already the indicated maintainer of pt_BR, unfortunately I got no answer there are some words, grammars and definitions which might need revision are you interested in correcting or at least reviewing it?
The translation was updated for the last release, which was very recent, so Frederico is still actively engaged. Send any patches you have via the translators' mailing list, thanks! http://lists.claws-mail.org/cgi-bin/mailman/listinfo/translators