Create MS Outlook-compatible Mail.app templates?

I have tried Mail Designer app (equinux) to create templates. Result after 2 hours of work:

1. They look great on a Mac and on an iPhone / iPad (as long as you don't alter them)
2. The look absolutely horrible on a Windoze PC (Outlook). 😠

It may be Microsoft's fault, but who cares when you create an e-mail whose text and graphics are totally garbled.

So, how can I design Mail templates that even a Windoze machine can render properly?

Thanks a lot!

Peter