Former Agreements with Owner

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I am a tenant that has rented the current property for almost 3 years now. The former owner asked me to leave by June 7, 2015 although our lease was to end through June. We agreed by email to leave by May 1st. It was an agreement. He sold the property to new owners. The real estate agent asked us to sign a tenant estoppel. She informed us that it was a confirmation that we were paying rent. She did not inform us that it would null any agreements we had with the previous owners. On April 1st, we gave our 30 day notice. The new owners responded to us on April 14th that regardless of our notice, we would be liable for rents due May and June. The real estate agents are not supporting us, even though they were a part of the email agreement. Had we known that we were not operating under that agreement anymore, we would have seen our lease through to the end. 

Am I liable?