The Microsoft issue described in the Knowledge Base article, KB316431, prevents OWA users from opening attachments to archived messages, when using forms-based authentication. To fix this issue, ensure that the following requirements are configured, if you are using OWA with forms-based authentication:

• Install ISA Server 2004 Service Pack 2.

• Request the Microsoft hotfix, KB924410, from Microsoft Product Support Services.

  To apply this hotfix, you need to run a script to add URLs to an exclusion list. Add the following URL using the script:

  ViewMessage.asp;
  

  Note that this is case sensitive.