Client SMTP Authorization (CSA)

Document Type Expired Internet-Draft (individual)
Author Dave Crocker 
Last updated 2005-10-17
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This Internet-Draft is no longer active. A copy of the expired Internet-Draft can be found at


Internet operation has typically required no public mechanism for announcing restriction or permission of particular hosts to operate clients or servers for particular services on behalf of particular domains. What is missing is an open, interoperable means by which a trusted agency can announce authorization for a host to operate a service. The current specification supports this capability for sending SMTP clients. Specifically, is a sending SMTP client permitted to act as a client MTA? Has a separate authority given it permission to perform this service? Client SMTP Authorization (CSA) specifies a DNS-based record that states whether an associated host has permission to operate as a client MTA.


Dave Crocker (

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