Outlook 2010 : is it possible to *keep* conversations open?
You can achieve this behavior by modifying your view settings.
In Outlook:
- View Settings:
- Group By: Conversation(ascending)
- Sort items by: Conversation (ascending)
- then by: Received (Descending)
- Sort items by: Conversation (ascending)
- Group By: Conversation(ascending)
Source: a comment in the discussion thread on answers.microsoft.com