You're not allowed to email the designers outside of 99designs from your contest. This is actually against our rules because by keeping communications on 99designs, it protects both yourself and the designers. Plus, we've built in a wide range of ways for you to communicate with your designers through 99designs.
You can contact any designer directly (very much like email) by sending him or her a private message.
Second, when running a contest, you can message designers both publicly and privately.
If you need an extension on your contest so that our designers can continue to submit revisions, simply contact support.