The Email Service Provider Coalition is now requiring its members to implement authentication for all email they send on behalf of clients - many of them marketers - ClickZ reports. ESPC will also mandate that members use authentication when sending their corporate email, it suggests that email senders immediately implement the IP-based Sender ID Framework, developed last year by combining Microsoft's Sender ID with the open source Sender Policy Framework (SPF).

Based on a recent survey of its membership, the ESPC found that 97 percent were authenticating outbound client email; and 73 percent were authenticating both client and corporate email. ESPC had previously required all new members to be compliant with the SPF standard and had urged existing members to become compliant.

ESPC members include Experian's CheetahMail, Constant Contact, Digital Impact, DoubleClick, ProspectivDirect, Return Path, Skylist, and StrongMail Systems. In April, it expanded membership beyond email service providers to include email infrastructure providers, mail transfer agents, internet service providers, nonprofits, anti-spam application providers and deliverability solution providers.