I'm pretty sure the one guy behind ai. doesn't justify that you change your regex for him. Let's not be overly pedantic.

> it's needed sometimes

When is this needed in the context of a Rails app? You never want to send emails to local hosts, and emails directly on the TLD is possible, but very little will work with them in practice.

> You never want to send emails to local hosts

That's not entirely true, it depends on how your mailing infrastructure is set up.

But in the context of a web app though? That's the key part: you're taking in email addresses from myapp.example.com. For other cases: sure, local email addresses can be useful (not often these days, but sometimes still are). But in this context I'm not really seeing any use case.

At previous $work, I wrote a rails app that managed releases. On the app you could sign up for email notifications when your change was released. These went through the unix local email system. So yes there is very much a use case

It's still a bit silly to tell every SaaS developer that they shouldn't validate that they have a normal-looking domain because some people's use cases call for sending emails to local addresses or to TLDs directly. If a developer needs to handle those cases, they know already, and they're in a vanishingly small minority.

Good to know. I guess I'll simplify again. Besides, I wonder whether the expression is vulnerable to catastrophic backtracking.

> Domains ending with a dot are valid though,

That doesn't mean you have to support their use. I have never seen a company support an email ending in a period and the world seems to continue along.