Generally when your lease expires and you remain in occupation paying rent you are deemed to be in a month to month lease.
Whether or not your email to the landlord agreeing to a new lease is binding upon you will depend on the fact scenario – is it a new lease or a renewal of lease? Are all the terms agreed or are the issues still to be negotiated? Does the email constitute an agreement in writing?
Your lawyer probably could answer that question once he/she has reviewed your correspondence and the facts.
From a practical perspective, I suggest you talk to your landlord. The world has changed. You may be able to renegotiate more suitable terms or explain that you can no longer afford the premises. Given the world has changed for the landlord as well they may be more negotiable and keen to keep you on as a tenant to protect their cashflow and the value of the investment property.
Trust the above helps.