The sending of a fax message provides a useful analogy: before a fax reaches its destination there is maximum uncertainty, which decreases with the arrival of each legible letter.

ECONOMIST: How (and why) to find a needle in a haystack | The

It can send a message to all message addresses (phone number, e-mail address, instant messaging screen name) for all message types (voicemail, e-mail, instant message, SMS, MMS, fax).

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