Understanding Domain types in Exchange Server 2010

Accepted domain is any SMTP namespace for which Exchange Server is responsible for sending or receiving emails. Accepted Domains fall into three categories.

1. Authoritative domain for which exchange hosts mailboxes

2. Internal Relay domain, also known as “Shared SMTP namespace” is generally used when companies are merged.

3. External Relay domain is used when one company is acting as an middle ware/ISP and forwarding it to the authoritative Exchange organization.