Are there privacy implications in the fact that when a recipient verifies a stamp they learn how many times the stamp was previously verified?
It is true that CentMail is giving the recipient a clue about the number of other recipients. If the sender wishes to fully conceal that information they should not stamp the message. Indeed, much of the point of stamping a message is to prove to the recipient that the message was not sent to them indiscriminately. • Who will run CentMail? Will there be competition for providing it? In addition to implementing CentMail ourselves (centmail.net), we are publishing the API as an open standard (see the appendix of our technical paper). We welcome other organizations to implement it and provide the service as well. • How can we incentivize the big players to agree to this? DomainKeys was adopted by Google and Yahoo! because of its promise to curb spam in the long run if it became a standard. We expect they have no less incentive to adopt CentMail. • Will companies pay for their employees’ emails? Most corporate email is internal and need not be certified. However, even if employees send ten
