@dcats,
Thanks, but the external Microsoft link has the wrong answer. We investigated this and are unable to prevent Exchange 2010 OWA from blocking MHT files.
Furthermore, the iPhone does not support MHT files either.
See Paul's comment on this thread: https://www-secure.symantec.com/connect/forums/mht-files-not-opening-blackberry-or-iphone#comment-2369641
Btw, here's the main post about the MHT issue in the Ideas forum: https://www-secure.symantec.com/connect/idea/sepm-scheduled-reports-file-format
(You can also search the Ideas forum for the other half dozen posts complaining about the MHT files.)
I was hoping you guys would finally drop the MHT files altogether in SEP 12.x. Unfortunately it doesn't look like that's the case, as the Ideas post says it was only partially implemented. Not sure what that means, but notifications come through as HTML messages. It's just the reports that are still using MHT files, which is disappointing. The whole reason for me to schedule a report to view in email is because I'm not at my normal desktop where I have normal access to the SEPM console. That means OWA and smartphones.