In some cases, users need to notify the same information to multiple recipients, with the requirement that these recipients have to send an acknowledgement of receipt. In this paper we present an optimistic protocol for multi-party certified electronic mail. A Trusted Third Party (TTP) can take part in a protocol run, but only in case of exception. Fairness is guaranteed for all parties being involved in a transaction. At the end of a protocol run, every party possesses enough evidence to prove the final state of the exchange. Parties can contact the TTP when they want (without temporal constraints). The presented protocol is the best one in terms of efficiency: only three steps have to be followed in the exchange sub-protocol.
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