You can “flag” a conversation as a reminder to follow up later.
Flag an active conversation
To flag an active conversation, click the flag in the top-right corner of the Conversation window. The flag turns red, making it easy to spot.
When the conversation ends, it is flagged in the Outlook Conversation History folder.
Flag a past conversation
In Office Outlook, open the Conversation History folder.
Click the flag next to the conversation, or right-click the flag to display a menu with more flagging options.
The Outlook Conversation History folder
By default, all conversations are saved to the Outlook Conversation History folder, where you can access them and forward them to others. When you flag a conversation, it is identified by a red flag. The Conversation History folder is typically displayed just above the Deleted Items folder in the Outlook Mail Folders list.
If you don't see the Conversation History folder, click the Options icon in the Communications Server Attendant toolbar. Click Options in the drop-down list, and then click the Personal tab. Under History, place a check mark in Save my instant message conversations in the Outlook Conversation History folder, and then click OK.