Confession on the telephone or by e-mail is not permitted by the Church for a couple of reasons. First, the sacrament of confession is a personal encounter with Jesus in which he:
personally addresses every sinner: "My son, your sins are forgiven." He is the physician tending each one of the sick who need him to cure them. He raises them up and reintegrates them into fraternal communion. Personal confession is thus the form most expressive of reconciliation with God and with the Church. (CCC 1484)
Second, maintaining secrecy is essential. The "Church declares that every priest who hears confessions is bound under very severe penalties to keep absolute secrecy regarding the sins that his penitents have confessed to him" (CCC 1467). E-mail, the Internet, and telephones are never completely private.
The Pontifical Council on Social Communications on The Church and Internet says:
Virtual reality is no substitute for the Real Presence of Christ in the Eucharist, the sacramental reality of the other sacraments, and shared worship in a flesh-and-blood human community. There are no sacraments on the Internet; and even the religious experiences possible there by the grace of God are insufficient apart from real-world interaction with other persons of faith. (9)