Quite s few getting this email. Just keep your phone on at all times in case they try to call you.xDid you apply with Priority?
They have stated that they're continuing to work on your application so they may just be running some checks, if they require further info from TUN then it could delay it as we all know that "Tunisian time" issue. They have to send such emails "we will be unable to decide your application within our customer service targets" to cover themselves.
Has your spouse been refused a visa before? Were you married previously (either of you)? Dont feel the need to answer on the open forum, if you dont want to, PM me if you'd like.