Earlier quoted context omitted.
I am actually appalled and baffled at American Express not applying case sensitivity. Like, what the actual.
I literally couldn't apply for an American Express card about 15 years ago because my (ISP) email address was too long. I wonder why they chose to restrict it rather than go with the standard email max length; they had to put effort in to pointlessly restrict new signups. Odd.
So I got a shirt that said "myself@iwenttodefcon7.andalligotwas.thislousyemailaddress.com"
Not too much later, I ended up working in software validation, and I broke so many login forms with that perfectly-valid address, I lost count.
Since then, Halibut Stuff dissolved and the forwarding service is long gone. If some HN reader wanted to set up a Mailinator-like service that generates absurd-yet-RFC-compliant email addresses for such testing, I think there might be a market.