We have a 6.0.8 network install on RHEL 5, 64 bit. Word and Excel docs are not behaving properly when attached to email. We have need to disable attachment saving for some remote users. When we set a user to "Disable attachment viewing from web mail UI" all works fine - preview disappears, and the download link leads to a permission denied warning.
When setting it to "Attachments can be viewed in HTML only", or for the matter when setting it to HTML or original format (the default), clicking on PREVIEW prompts the user to download or open the attachment, rather than showing me the HTML in line preview.
This behavior has been seen in the latest Chrome, Firefox plus IE 8 on Windows. I haven't tested other browsers, or on a Mac, but it doesn't matter, since this is already bad enough.
Release 6.0.8_GA_2661.RHEL5_64_20100824100342 RHEL5_64 NETWORK edition.