We recently gave an overview of Yahoo's Domain Keys proposal, an anti-spam open-source system that uses public key cryptography to digitally sign e-mail and verify its origins. However many anti-spam crusaders aren't thrilled by the idea of putting such plans into the hands of the mega-ISP's. As this Business Week On-line article explores, there's a growing number of anti-spam experts finding fault with Yahoo's plan. Among the concerns are thoughts that DomainKeys would be vulnerable to "Replay attacks", where spammers steal a digital signature from a verified e-mail and use it as phony authentication. There's also simply an undercurrent of dislike across many anti-spam mailing lists for mega-corporations and ISP's (with marketing relationships and "legit" mailers to protect) taking the reins on such a project. Yahoo suggests the open-source nature of the project should indicate they're willing to move forward with community support.