Should email validation requires the domain part contains a dot?

Question

I noticed that the built-in browser validation for <input type="email" /> requires a format of xxx@xxx. Only the @ character is required. There is no need to a dot, like [email protected].

It is the same with the popular jQuery.inputmask, the rule of email alias does not require the dot, either.

I am just curious. Is it a standard way to ignore the dot in email validation now? I haven't seen any email address on the root level domain. What is the reason to ignore the dot?

Threegaited

possible duplicate of Why does HTML5 form-validation allow emails without a dot? – Rebeccarebecka

emails are complicated, almost anything containing @ could be an email, even bill@com, which is why validating too strict tend to lead to problems. – Emee

Thanks, Juhana. It appears to be duplicate. – Threegaited

Play framework requires a dot in the domain, unfortunately, since MS userPrincipalName (also based on RFC-822) validates without a dot. – Kentonkentucky

Answer 1

The RFC 822, chapter 6, gives the specification of an address in augmented Backus-Naur Form (BNF):

addr-spec   =  local-part "@" domain
local-part  =  word *("." word)
domain      =  sub-domain *("." sub-domain)

Using this specification a@b is a valid address.

Matsumoto

The spec is stupid, because every email address in real life has a .com, .net, etc. It is a somewhat common user error to forget that ending, so in real life, following the spec means a lot of faulty email addresses get accepted. – Phlogistic

@Acyra, the spec is not stupid at all, since user@localhost is a perfectly valid email, and so is something like user@com. An example of the second type, where a TLD can point to something is the domain uz as of Oct. 2018. See results for nslookup uz if you're curious. – Silurid

I was trying to use a built-in validator in .NET and it allows user@localhost like you said. But, I agree with Acyra, it's stupid. That case is very rare. So email validators that are built in to a framework should at least give you the option to require the top-level domain (maybe even default to requiring it and allow for no top level domain as an option). In my code, I don't want to allow localhost or an IP address as the domain. – Amatruda