Suggest alternate forum/exchange when “off-topic”?
Many posts are posted only in stackoverflow. Some of them are closed because they are not relevant to stackoverflow. In that case moderators should redirect to it's corresponding sites like 'codereview.stackexchange.com', 'webapps.stackexchange.com'. By that way you can attract more audience to those sites and make user happy. But these redirects should be handled with care OR moderators should suggest one or more sites that are relevant to that question before closing them.