I've never had a problem with GoDaddy email until this year. Earlier this year I had problems sending mail from Outlook. After weeks of that on and off, I finally called them. They said it's a Microsoft issue and suggested I change the out port in Outlook because the out port I was using was being overwhelmed. That made sense. If Outlook programs all over the world are trying to send over and over again, it would be hard on the server.
I changed the email addresses in the WA code to yahoo for Classic Pumps and gmail for Webs by Wagner. It's not a good solution because those are not primary emails for either of us.
Are you saying you know of no reason your code should not be compatible with the latest version of PHP? That's really the bottom-line here. All servers were responding just fine for years with these forms. Suddenly I have problems when HostGator updates.