Invalidity dossier
US 6035327
SMTP extension to preserve per-message and per-recipient properties
Current assignee: Microsoft Technology Licensing LLC
Added 9/23/2026, 3:30:38 PM
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Patent summary
Title, assignee, inventors, filing/issue dates, abstract, and a plain-language overview of the claims.
Patent Overview: US6035327A
Title: SMTP extension to preserve per-message and per-recipient properties
Patent number: US6035327A
Application number: US08/987,338
Inventors: David Buckley, Donald Gordon Brown, Wayne Merl Cranston
Original assignee: Microsoft Corp
Current assignee (per listing): Microsoft Technology Licensing LLC
Priority/filing date: 1997-12-08
Publication (grant) date: 2000-03-07
Legal status (as listed): Expired – Lifetime; anticipated expiration 2017-12-08
Source: https://patents.google.com/patent/[US6035327](/patent/US6035327)/en
Purpose. The invention extends email protocols used between mail servers—specifically SMTP (defined in RFC 821) for transferring RFC 822 messages—so that additional data not defined in those protocols can be carried along. The problem addressed: custom data fields allowed by many networks are lost when a message crosses the Internet, because SMTP and the 822 message format lack support for custom information. The present invention uses the private-extension mechanism of RFC 1869 to let a sending server discover whether a receiving server supports the desired extension.
Plain-language scope. A sending server decides whether extra information should be sent, obtains it (e.g., extracted from the 822 message or from another source), and encodes it—covering both per-message and per-recipient information—into a single mutually understood data stream. It contacts the receiving server, elicits supported SMTP extensions, and checks whether the invention's extension is supported. If not, normal 821/822 transfer proceeds without the extra data. If supported, the server sends the 821 envelope information, then the additional data via the extension, then the regular 822 session, then terminates the connection. The added information may comprise message "properties" (message body, "To", "CC", etc.).
Not established by this excerpt. The excerpt does not establish the full claims, the detailed encoding format (text is truncated mid-sentence), specific figures, litigation, validity, or prior art beyond cited RFCs 821, 822, and 1869. Ownership and legal-status entries are stated as listings, not legal conclusions.
Generated 10/1/2026, 9:51:32 PM
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Litigation summary
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PTAB challenges
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Assignment history
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Prior art
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Obviousness
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Extensions
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Derivative works
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