No email can supersede the boundaries of the written contract. Let THEM spend their money. I wouldn't spend a dime.

Discussions of terms, whether over the phone or in e-mails, aren't legally binding.

Think it out ... if you send an e-mail asking for a 20% reduction in price and the seller fires back with a "NO" ... which one do you accept as binding? If several closing dates are discussed, which one is the real one?

Unless the parties actually AGREED with each other and said something like "We agree on A, B, C and that D will not be done. We'll send the paperwork over tomorrow." It's hard to get negotiations accepted.

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You may want to fire back with "by failing to get a mortgage commitment the buyers were not negotiating in good faith".

Go tell them to pound sand!

Assuming your potential buyers put up "earnest money" in escrow, if they fail to fufill the terms of the purchase agreement which you both signed, they may be liable to forfit the earnest money to you. That may be what all of this is about: to try to get their earnest money back.

If you took your house off the market after accepting and signing a purchase agreement, and they now wish to back out of their purchase agreement you may have grounds for damage, assuming you can prove loss.

Good luck on your project.