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Should Exchange Server utilize the SMTP connector for internal email?

SearchExchange.com expert Richard Luckett describes the circumstance in which an Exchange server may not recognize internal mail messages.

I have two Exchange 2003 servers in my environment. Both are located in the same administrative group and routing group. I have an SMTP connector with address space * and a smart host specified to carry the Internet mail. Both servers are bridgeheads for the connector.

Should the internal email (coming from my domain and destined to my domain) go through this connector based on the * in the address space, or will Exchange Server realize that the recipient is in my domain and not utilize the SMTP connector? I saw a few internal email messages utilizing this SMTP connector. Have you seen this before?

Internal mail should not utilize the SMTP connector. However, if the sender uses an outdated email address, Exchange Server may treat that recipient as an external SMTP address and try to get DNS to resolve it externally. A good example of this would be a user replying to an old email or using personal address book after a mail migration.

The actual message handling architecture of Exchange Server 2003 requires that all email messages be categorized. Categorization expands distribution groups and queries Active Directory (AD) to see if the recipients in the To: line matches any mailboxes within your Exchange Server organization. If, and only if, the email address is not found in AD will Exchange Server query a public DNS server, or route to a smart host for external name resolution.

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