changed

          <label for="settingForm[mail.from]" class="col-xs-3 control-label">Fromアドレス</label>
to
          <label for="settingForm[mail.from]" class="col-xs-3 control-label">{{ t('app_setting.From e-mail address') }}</label>

lib/views/admin/app.html

@@ -87,7 +87,7 @@
       <p class="well">{{ t("app_setting.SMTP_used") }} {{ t("app_setting.SMTP_but_AWS") }}<br>{{ t("app_setting.neihter_of") }}</p>
 
         <div class="form-group">
-          <label for="settingForm[mail.from]" class="col-xs-3 control-label">Fromアドレス</label>
+          <label for="settingForm[mail.from]" class="col-xs-3 control-label">{{ t('app_setting.From e-mail address') }}</label>
           <div class="col-xs-6">
             <input class="form-control" type="text" name="settingForm[mail:from]" placeholder="例: mail@crowi.wiki" value="{{ settingForm['mail:from'] }}">
           </div>