There really aren't that many moving pieces, and smtp is one of the more forgiving protocols in use on the internet I think the moving pieces are on the other

There really aren't that many moving pieces, and smtp is one of the more forgiving protocols in use on the internet I think the moving pieces are on the other side and the person you're trying to email doesn't know what those pieces are -- even if you can see that their mail server is rejecting your email, that person doesn't usually know who to talk to to find out why. Even if you can convince them to open a support ticket with IT, their first level IT support doesn't know what to do either, you'll get responses like "Our IT department wants to know what version of Outlook you're using? And they said you should trying rebooting your computer".