System, method and program to limit rate of transferring messages from suspected spammers

A computer system for managing e-mails, the e-mails being received at a firewall or router en route to a mail server, the computer system comprising:

• one or more processors, one or more computer-readable memories, one or more computer-readable tangible storage devices, and program instructions stored on at least one of the one or more storage devices for execution by at least one of the one or more processors via at least one of the one or more memories, the program instructions comprising:
• program instructions to determine a first score indicating an extent to which contents of a first e-mail sent by a first source exhibit characteristics of spam, and in response to the first score exceeding a lower threshold but not exceeding an upper threshold, limit a rate at which the firewall or router forwards the subsequent e-mails from the first source to the mail server, the rate limit being predetermined, greater than zero and less than a maximum rate at which the firewall or router is able to forward e-mails from the first source to the mail server absent the rate limit;
• program instructions to determine a second score indicating an extent to which contents of a second e-mail sent by a second source exhibit characteristics of spam, and in response to the second score exceeding the upper threshold, cause the firewall or router to block from the mail server subsequent e-mails from the second source destined for the mail server;
• and
• program instructions to determine a third score indicating an extent to which contents of a third e-mail sent by a third source exhibit characteristics of spam, and in response to the third score being less than the lower threshold, allow the firewall or router to forward subsequent e-mails from the third source to the mail server without blocking or rate-limiting the subsequent e-mails from the third source based on the contents of the third e-mail.