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What do you mean mail things? You're not supposed to connect anything directly to a telephone line, it's illegal in the US it may be so in other countries as well. http://www.electro-tech-online.com/custompdfs/2009/03/CI-2-DTMF.pdf
Shows one method of interfacing an MT8870 to a phone line. The capacitors are for isolation and the zeners are to shunt any voltage spikes.