Problems receiving messages with attachments

[Laurie]

I use Eudora Pro 4.0, my email messages have a signature. When I send to clients who have Outlook 2003, and send the message with an attachment, they can not read my message. They can read it in the preview window only, but not on the screen itself. I am looking for a way to correct this problem for them. If I send it to an Outlook 2002 user, there is no problem
Thank you.