message. Telex Link added the necessary Telex codes as required and tried to send the message as many times as required before positively confirming receipt by means of a special Mailbox message. Telexes could be sent to Prestel Mailbox users from a standard Telex terminal by using Telex Link number and inserting "MBX" and the relevant mailbox number as the first line of the telex message itself. The incoming telex message appeared to the Prestel recipient just as an ordinary Mailbox message but with the telex number inserted at the top of the frame. Because of the charges inherent in use of the Telex service, messages sent via Prestel Telex Link were chargeable, in 1984 at the rate of 50p for destinations in the UK, £1.00 for Europe, £2.00 for North America, £3.00 for elsewhere and even £5.00 for sending to ships via INMARSAT. There was no charge to Prestel users for receiving Telex messages. In the same year, when there were some 70,000 users registered, up to 100,000 mailboxes and telexes were sent each week via Prestel Mailbox. From July 1989, a new mailbox system was introduced which allowed for single messages of up to five frames in length, storing of messages prior to sending, sending to multiple recipients, either individually or via a mailing list, forwarding of messages, and requesting an acknowledgment of receipt. Whilst sending a simple mailbox using none of the new facilities remained free, all of the new options were charged at 1p per use per recipient. For the first time, the sending of spam was accounted for and permitted, albeit at 20p per recipient. In addition, the stored message facility was replaced by a summary page, which listed all the messages, both new and old, that were waiting. The user could then pick which message to view, rather than being required to read through them all in chronological order. As only the first 20 could be accessed, this effectively allowed for up to 19 messages to be stored while allowing the continued reception of new mail. A security breach of the Prestel mailbox of the Duke of Edinburgh and subsequent trial led to the Computer Misuse Act 1990. Public take-up While teletext services were provided free of charge, and were encoded as part of the regular television transmissions, Prestel data were transmitted via telephone lines to a set-top box terminal, computer, or dedicated terminal.