In 2 days from now, users of legacy versions of our client-side software will no longer be able to login due to forced SSL setup update server-side. the error message will be cryptic. Also, we don't have the email of all such users hence can't easily communicate with them.
Is it acceptable practice to ask a question on superuser.com (with error screenshot) and answer it ourselves (tell user to upgrade)? The idea is that superuser.com is well indexed and page ranked hence would show up high in results of users looking up the error message.