I finally found the actual patents, they are discussed in this story:
http://www.siliconvalley.com/mld/siliconvalley/business/columnists/mike_langberg/5565050.htm
According to the story both patents are currently owned by MailBlocks, Inc.
The patent numbers are US# 6,199,102, filed August 26, 1997 and issued
March 6, 2001; and US # 6,112,227, filed on August 6, 1998 and issued
August 29, 2000. Both patents can be looked up at the website of the US
Patents and Trademarks Office (http://patft.uspto.gov/netahtml/srchnum.htm).
Abstract of patent # 6,199,102:
A method is provided for preventing the delivery of unwanted electronic
mail messages to a destination client. An original electronic mail message
is first received from a source client at a destination server. Next, a
reply electronic mail message is sent from the destination server to the
source client requesting the source client to complete a registration
process to register the source client's electronic mail address with the
destination server. The original electronic mail message is only sent from
the destination server to the destination client when the source client
properly registers the source client's electronic mail address.
Abstract of patent # 6,112,227:
A method is provided for preventing the delivery of unwanted electronic
mail messages to a destination client. An original electronic mail message
is first received from a source client at a destination server. Next, a
reply electronic mail message is sent from the destination server to the
source client requesting the source client to complete a registration
process to register the source client's electronic mail address with the
destination server. The original electronic mail message is only sent from
the destination server to the destination client when the source client
properly registers the source client's electronic mail address.
The second one seems to cover all C/R systems and that's what MailBlocks
claims in the news article.
Yakov
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Yakov Shafranovich / <research(_at_)solidmatrix(_dot_)com>
SolidMatrix Research, a division of SolidMatrix Technologies, Inc.
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"One who watches the wind will never sow, and one who keeps his eyes on
the clouds will never reap" (Ecclesiastes 11:4)
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