Using classic Outlook for Windows in business environments
Our issue has been occurring for approximately 2 weeks now. I contacted Yahoo, and they stated it's either Microsoft or our host (GoDaddy), and GoDaddy states there is nothing wrong on their end. Microsoft doesn't seem to be taking this very seriously.
Who knows where the problem is originating, but it seems to be somewhat widespread, so it would be nice if whoever's system is causing it would do something to fix it. Especially since we are unable to communicate with our customers who have a Yahoo email account, I'm confident we are not the only company dealing with this right now.