Would it be possible to have Slick Contact Forms save all the feedback in DB? This would be the most handy place to look for it. This would also be worth it's code weight in gold in cases when there's a problem with emails. An additional benefit is that the feedback that a site has gathered will be backed up at the same time as the rest of the site.
The code and user interface of Contact Form 7 to Database Extension are an excellent example. The same plugin also saves Fast Secure Contact Form's submissions to database, but unfortunately doesn't support Slick Contact Forms.