Newsletter Email not sending in Publisher 2007

I create newsletters for my business and send them out to customers.
Currently, I use Publisher 2007.

Until about a month ago, I never have had an issue with them being sent via
email.

This past week, I created two new newsletters and sent them out using
Outlook 2007.

The email appears to send without any problem.

The problem is that although Outlook says it was sent, but the message was
never delivered. I've tried this with all three email addresses on my
computer, and cannot get delivery receipt, or even receive them myself.

I've got two different types of email accounts on my PC, one which is
directly thru my ISP, the other thru the company website host. I can
sometimes get the message to be delivered if I send if from my ISP email
account to the website host email, but not the other way around.

I receive no errors or warnings or anything, so this problem has been rather
stressful to troubleshoot.

When I send an email from any of the accounts WITHOUT the Publisher file,
the email comes through without an issue. (Even when I select "Send as
attachment" in publisher)

So, the problem only appears when I choose the "Send as a message" option
within Publisher. This also makes the tech support folks at my ISP and
webhost think I'm insane.....

HELP!