I thought I had this solved. Without my changing anything, it started up again. I tried changing the
"retVal.Configuration.Fields("http://schemas.microsoft.com/cdo/configuration/sendusing") = 2
retVal.Configuration.Fields("http://schemas.microsoft.com/cdo/configuration/sendusing") = 1
but that didn't work...
So far we have narrowed this down to it being a problem with our mail server. We use our own mail server and our admin has set it up so that "outside" email addresses (confirmation emails to customers) are not allowed to relay through.
If the email is an accepted email on the server it gets sent out. If it's not an email from our own domain, it gets blocked. So, essentially, EVERYONE but employees are blocked. We could just open it up, but then we get "black-listed." It's my understanding that every spammer will be able to freely pass through.