From the Lotus.com web site:
Domino and Notes 4.6 Maintenance Engineering Support and End of Service
Based upon input and requests from customers and partners around the world, Lotus extended maintenance engineering support of the Domino and Notes 4.6x codestream until January 31, 2002. Although the release of R4.6.7 in March 2000 marked the end of the regularly scheduled Maintenance Releases (MRs) for the 4.6x codestream, periodic, unscheduled Maintenance Updates (MUs) for 4.6x were extended for another year. January 31, 2002, is the End of Life (EOL) date for 4.6x, superseding the previously stated EOL date for 4.6x of January 31, 2001 (as announced in the 4.6.7 QMR announcement of March 2000 [technote #179124 ]).
End of Service
Accordingly, telephone support for 4.6x was extended to a minimum of 12 months beyond the introduction of the last 4.6x MU, which will bring the full time period of support for the 4.6x releases to almost five years. The End of Service (EOS) date for Domino/Notes 4.6x, therefore, is confirmed as January 31, 2003, as documented in "Lotus Customer Support Process and Dates for End of Live Product Support" (#157820 ). You can submit a request to purchase an IBM Service Extension to extend phone support beyond this date if desired. For more information, contact your sales representative or your Lotus Service Manager if applicable.
An exception is the Notes 4.6x client on the OS/2 platform. The End of Service (EOS) date for Notes 4.6x on OS/2 only is December 2004.