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 had a company I was doing business with reject a valid email address of mine because it contained a “.” character in it. I got an error message about this being invalid email address to use. My “first.last@emailprovider.com” address had no problems sending/receiving emails with anyone else.
There should be some simplified standard way to identify what combination of email configuration is/isn’t supported by companies and email providers. This can also future proof against future changes in email configuration changing over time due to the ongoing fight against spam.
There’s already a standard that defines what is an acceptable email address. And an standard reply for a rejected email address.
The issue is you’re dealing with a misconfigured or inappropriate email stack.
Yep. This happens when some idiot tries to roll their own regex. I’ve also seen them frequently reject my+email@domain
Email address regex: ‘.+.+’
Joke, here’s some reading on it. Basically, E-Mail address can have almost any form and you better use a library that doesn’t use regexp parsing.
My favorite is when you do “first.last+company@domain.com” and they come back saying it’s an invalid email. But “first.last+somethingelse@domain.com” works just fine. Meaning they are looking for their company name in the email and hard failing on it.
The one I am thinking of in particular also failed with “company@domain.com”.