Hi,

Does this happen on more than one site? Have you tried renaming the file to .doc?

Thanks for the prompt reply. I just discovered that if I forward the mail sent to my usual e-mail (Philippe.Gavillet@cern.ch) to my 2nd email (Philippe.Gavillet@gmail.com), I can open/download normally the attachment from the later. I deduce that the problem is linked to the settings of my usual e-mail address.

Note: I had tried to rename the file from attachment.ashx to attachment.doc without success.

                                                                      Thanks for your help

Outlook Web Access sends an illegal Content-Dispositon header to Firefox. This is no longer allowed in Firefox 8. Firefox 9 will have a workaround for this so that Microsoft has time to fix their software.
See http://support.mozilla.com/nl/questions/895024
https://support.mozilla.com/en-US/search?q=attachement.ashx
Bug 704989 - add workaround for broken Outlook Web App (OWA) attachment handling