Outlook having trouble handling email with HTML content.

Hi

I am baffled. I am supporting a user. Using
MS Vista Business with Office 2003 SP3. Mozilla installed as browser.

Problem: Whenever forwarding a message with HTML content outlook freezes for 2 to 3 minutes. Only then can the message be sent/forwarded. I unticked the option “User Word as default text editor. Toggled between rich text and HTML in Mail Format options.

Tested emails with and without attachments, no joy.

Any suggestions please??