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How do servers (both SMTP and X.400) communicate link state information between routing groups?

April 26, 2017Communicate groups link routing servers SMTP State x.400

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How do servers (both SMTP and X.400) communicate link state information between routing groups?

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When two servers communicate through SMTP, Exchange 2000 uses a version of LSA protocol that works as an extension to SMTP through the SMTP Service Extensions (ESMTP) framework. Exchange 2000 servers advertise X-LINK2STATE support during the EHLO. When one Exchange 2000 server sees another advertising that, it attempts to trade routing information. Routing information will only be traded if the two servers are in the same organization (a DIGEST string is compared). This only occurs in the event of per-routing-group differences in transferred information. Between routing groups, when servers communicate through X.400, Exchange 2000 uses a version of LSA. The MTA constructs a “dummy” X.400 message to transfer this information.