Thank for the tip Eric, I didn't know I could check the PHP version that way. I did start a support ticket and they told me to contact Bluehost and get them to look at the email logs for the issue. They think that it may be a SMTP setting that Bluehost needs. You pointed that out and sent me the link to the page with that info.
I will talk to Bluehost to see if they can provide me with the info I need. I was thinking though, if it is a SMTP issue, wouldn't all the emails addresses specified in the from settings be affected, not just one of them?
Thanks
Onward Through The fog!