If you install TFS and don't specify an e-mail address, you'll receive the following error in your Applicatoin event log:

Event Type: Error
Event Source: TFS Services
Event Category: None
Event ID: 3031
Date:  17/08/2006
Time:  09:58:46
User:  N/A
Computer: TFS Server
Description:
TF53010: An unexpected condition has occurred in a Team Foundation component. The information contained here should be made available to your site administrative staff.
Technical Information (for the administrative staff):
Date (UTC): 17/08/2006 08:58:46
Machine: TFS Server
Application Domain: /LM/W3SVC/3/Root/services-3-1280027870957xxxxxx
Assembly: Microsoft.TeamFoundation.Server, Version=8.0.0.0, Culture=neutral, PublicKeyToken=xxxxxxxxxx; v2.0.50727
Process Details:
  Process Name: w3wp
  Process Id: 2172
  Thread Id: 3204
  Account name: domain\TFSService

Detailed Message: Unrecognized default notification 'From' address:

To fix this, add an e-mail address to <add key="emailNotificationFromAddress" value=TFSemailaddress@company.com /> in C:\Program Files\Microsoft Visual Studio 2005 Team Foundation Server\Web Services\Services\web.config