Email Not Arriving via IE6

I have a free email account at a popular web site/search engine/etc. After I’ve logged into my account, composed an email, and Sent it, the body or text message doesn’t arrive at the destination. Contacts have replied wanting to know what’s the message. Attachments arrive OK. I’m unemployed and use it for sending resumes. I’m using XP Professional, IE6 web browser with default settings. I have stayed current with all of the Windows Updates. The problem started before I installed SP1 and continues after downloading it. I then downloaded the Sun Java software in hopes that would fix it, no luck. I contacted the email host and they said they’re looking into it. Also, about every fifth email arrives at its destination OK. Does anyone have an idea or a fix for this? Thanks.