Consider also asking for amended lease with better terms.

Thank You TennisDaze

If you're saying the the lease is expired (because they didn't timely extend), shouldn't the burden be on them now to prove you're wrong? I would think whether or not they do in fact still have a valid lease hinges on the postmark date. If you get push back, and depending on how much lost by not leasing at current rates, you might want to get an attorney involved.