A micropayments method and apparatus to control spam using a centralized server architecture. The central server receives requests from senders who want to send emails, and determines if the sender has a micropayments account with an adequate balance. If so, an encrypted stemp is sent back to the sender and the amount of micropayment is deducted from the account or transferred to the recipients account. The key and a serial number of the message is saved in the server. The recipient computer receives the email, sends the serial number to the server and requests the key. The key is looked up and sent back to the recipient. Many alternative embodiments are disclosed such as centralized stemp decryption, centralized white lists, decentralized key decryption, one key used all the time for a particular recipient, transfer of value to recipient only upon opening message, etc.
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