A client using Outlook 2003 sends distribution lists weekly to all staff - they delete the existing one and update with the new one. This week no one could access them, they all arrived as dat files. Both 'ends' have Outlook set to send in html, sender has tried sending using Outlook as editor and Word. I had her send me a test as well (I use Outlook 2003 as well), same problem. The problem is also happening when she attaches a single contact as a vcard - it arrives as a dat file. Has anyone had a similar experience and figured it out?