The product from Anodyne Developments uses software that blocks spammers unless they are willing to pay a fee.
Attempts at filtration have so far been unsuccessful because the spammers keep finding ways to get round the software. Anodyne's product allows e-mails through only if the sender is on a list of permitted correspondents.
The list resides on the user's ISP server. E-mails from unlisted senders will be directed to a micropayments site to pay a fee.
The software reads and stores addresses in outgoing e-mails so that a reply can be returned without being blocked.
Andy Dwelly, chief executive of Anodyne, admitted that many unsolicited e-mails are enquiries about purchasing goods and services, but said users outside the sales and marketing teams could benefit.