Of the vast majority of codes involving sending from excel, the line for changing importance is typically not there. You could try commenting it out and see if you still get the same results.
'.Importance = olImportanceNormal
Or could you have the options set on your email to send messages with low importance?
From the Outlook 2003 help files
1. On the Tools menu, click Options
2. Under E-mail, click E-mail Options.
3. In the Email Options dialog box, click Advanced Email Options.
4. Under When sending a message, in the Set importance list, click High or Low.
Hope this helps you