It would be useful for those maintaining domains and networks to be able to specify that individual hosts or nodes are authorized to act as MTAs for messages sent from those domains or networks. This working group will develop a DNS-based mechanism for storing and distributing information associated with that authorization. The primary current use case for this facility is to allow recipient MTAs to confirm that peer MTAs' actions are authorized by specific domains or networks. This will help combat a certain class of domain forgery common in spam. The solution chosen, however, should be generally useful for others which might check this authorization data. This working group is being chartered after extensive discussion of the issues in the IRTF's Anti-spam Research Group, and it is presumed that all active participants will be familiar with the documents produced there which describe the problem. It is not, however, an extension of that research group; it has no general writ to study spam or to produce specifications on the topic. It will not consider anti-spam abatement measures outside of the area of MTA authorization. Because individual messages may be associated with multiple domains (among them the domains present in the RFC2822 From, RFC2822 Sender, the SMTP Mail-From, and the SMTP EHLO), the first task of the working group will be to establish which of these identities should be associated with MTA authorization. Once this decision has been reached, it will limit the scope of further activity in this working group, and the chairs will rule out of order discussion related to schemes which use other identities as the basis of authorization. The groups Technical Advisors will help ensure that the semantics of proposals originating within this group are consonant with DNS standards and syntax, and they will be available for early cross-review to ensure that this work proceeds at an appropriate pace. Upon chartering of this working group, the IESG intends to request that the IRTF Chair and the Chairs of the IRTF's Anti-Spam Research Group seek publication of the listed input documents as Experimental RFCs, so that they are available on an archival basis. The IESG also intends to request that the RFC editor insert a note into each document informing the reader that the IETF's MARID working group has taken on the task of producing a standard in this area.