so you give the estate agent a message to communicate back to the buyer?
the formal way of communicating in such an instance is on the contract of sale. If it aint in writing, on the contract of sale, with your signature, to the buyer its just more guff and hot air from the estate agent.
Put yourself in the buyers shoes, where are you more likely to counter offer/offer again, when the estate agent comes back and tells you this offer is rejected, but would be happy to consider offers closer?
Or when a counter offer, in writing, and signed by the vendor comes back to you?
It doesnt happen as much anymore, but years ago, it was extremely rare to get a contract of sale that wasnt crossed out and initialed at least twice. I guess it must be estate agents who didnt like conveying offers around all the time....