XIMS: Internet Mail Containing Null Originating Address of Mail From:<> Is Rewritten by the Internet Mail Service as <Unknown>

When Internet mail arrives that has a null From address, the From address is changed from "Mail From:<>" to " Mail From:<unknown>" if the following conditions exist:

• The Internet Mail Service is configured to forward all messages to a particular Simple Mail Transfer Protocol (SMTP) host.
• The routing is configured with either the Do not Reroute incoming STMP Mail or Reroute incoming SMTP Mail option set and the SMTP domain accepted as incoming.
• A custom recipient exists in the global address list for a user in that domain.

For example, assume following conditions exist:

• The SMTP host is smtp.microsoft.com with a user account "user@microsoft.com."
• A Custom Recipient (Internet mail) is created on the Exchange Server computer for user@microsoft.com.
• In the Internet ConnIMC properties, on the Connection tab, Forward all messages to host is selected with the value "smtp.microsoft.com," and on the Routing tab Do not Reroute incoming SMTP Mail is selected.

When Internet mail arrives with a null From address ("Mail From:<>") to user@microsoft.com at the Internet Mail Service connector, the Internet Mail Service accepts the mail and tries to forward the mail to smtp.microsoft.com, but the From address is changed from "Mail From:<>" to " Mail From:<unknown>."

To resolve this problem, obtain the latest service pack for Exchange Server 5.5. For additional information, click the following article number to view the article in the Microsoft Knowledge Base:

Microsoft has confirmed that this is a problem in Microsoft Exchange Server Version 5.5. This problem was first corrected in Exchange Server 5.5 Service Pack 4.