Viva.com, one of Europe's largest payment processors, sends verification emails without a Message-ID header — a requirement of RFC 5322 since 2008. Google Workspace rejects them outright. Their support team's response to my detailed bug report: your account has a verified email, so there's no problem.
I blame the processor on this. Yeah the whole debate on if it is mandatory by the rules is there but common. Your a major business. You want your things as properly done as possible including email.