As specified in [MS-ADTS], domain controllers (DCs) use the Directory Replication Service (DRS) Remote Protocol (as specified in [MS-DRSR]) to replicate their configurations, schema, and domain naming context (domain NC) to other DCs. DCs are usually configured to use Directory Replication Service (DRS) over a remote procedure call (RPC) transport mechanism; however, in some environments, RPC transport is unsuitable (for example, if firewalls in the network between the DCs are configured to block the ports used by RPC).
This document defines the extensions to the DRS Protocol for transport over Simple Mail Transfer Protocol (SMTP). These DRS Protocol Extensions for SMTP provide an alternate transport for the DRS Protocol that allows DCs to perform replication in environments where the RPC transport mechanism is unsuitable. As specified in this document, the DRS Protocol Extensions for SMTP encapsulate the DRS messages into MIME attachments (as specified in [RFC2045]) that are then sent through email between DCs by using SMTP (as specified in [RFC2821]). This document does not define extensions or changes to the SMTP protocol itself.
Sections 1.5, 1.8, 1.9, 2, and 3 of this specification are normative. All other sections and examples in this specification are informative.