Keeping track of communication threads

I've been trying to figure out how to group all the communication revolving around one topic. The topics are not on-going, as in over weeks and months. However, frequently, numerous people reply to an email over the courser of a few days but not in sequence.

How can I group them together or do something that keeps me keep track of all of them so I can reference?

The way to do this is to group your messages by conversation. To do this in Outlook 2003 and Outlook 2007 choose;
View-> Arrange By-> Conversation

Outlook 2010 has a new Conversation view which can be enabled via; tab View-> option Show as Conversation

If you want to combine this with your own sent items or when the messages have been scattered amongst different folders, you can use a Search Folder which includes the Inbox folder and the Sent Items folder (and any other folder you might want). If you are using Outlook 2010, you can directly set this via an option.

Outlook 2003 and Outlook 2007 – Conversation across folders

To create a Search Folder containing messages from other folders choose;

  1. File-> New-> Search Folder
  2. Scroll down and choose "Create custom Search Folder"
  3. Click "Choose..."
  4. Name the Search Folder. For instance: Conversations
  5. Click "Browse..."
  6. If you want to search in your entire mailbox leave the selection of your root folder and the "Search subfolders" option. If you want to search all your Inbox and Sent Items folders, deselect the root folder and select the Inbox and Sent Items folder. If you don't want to search subfolders of the Inbox and Sent Items folder, deselect the "Search subfolders" option.
  7. Press "Ok" until you're back to the main Outlook window.
  8. Select the just created "Conversations" Search Folder and set the view to Group By Conversation

Outlook 2010 Conversation View settings

In Outlook 2010, you can do the above by pressing the Conversation Settings button on the View tab and selecting the option; Show Messages from other Folders.

Outlook 2010 - Conversation Settings - Show Messages from Other Folders
Conversation view settings in Outlook 2010.