How to turn off conversation threading in Lotus Notes
In Lotus Notes 8.x client, you have to use:
File -> Application -> Properties Advanced (tab)
and then uncheck "Support Response Thread History"
In Lotus Notes client
File -> Database (mail database) -> Properties -> Advanced (tab)
un-check "Support Response Thread History"
or
In Mail Database
Click on "Show" button -> Individual Messages
IBM Notes 9: Social Edition
Turn off conversations
Actions -> Individual Messages (Alt + A + I)
Turn on conversations (mail grouping)
Actions -> Conversations (Alt + A + R, R, Enter)