Scot Desort wrote:

I have a customer who just upgraded to Outlook 2007 running under
Vista. She was previously using Outlook 2003 on XP.

Her default email composing format is set to HTML in Tools, Options,
Mail Format.

She has a contact group with 37 email addresses in the group.

When she composes a new message to the group, it is being sent in
RICH TEXT format, making attachments inoperable for recipients not
using Outlook.

Let me guess - she imported her contacts from the previous version. Have
her open one of the contact items representing one of the people who receive
the Rich Text messages. Double-click on the email address to open the
"E-mail Properties" dialogue. Examine the "INternet mail format" drop-down
at the bottom. It should contain "Let Outlook decide the best sending
format". If it contains "Send using Outlook Rich Text format", that's the
problem.
--
Brian Tillman [MVP-Outlook]