Add ValidationRule to disallow whitespace in the local-part and domain

[rohannagar]

Add ValidationRule to disallow whitespace in the local-part and domain

[PascalSchumacher]

Thank you very much for the in-depth explanation.

I wasn't aware that white-space is allowed in some places. I noticed that email addresses like these are either rejected by Java Mail or by Apache James Mail Server.

I will use the rule you suggested and later update the code to use the build-in check when/if you add it to JMail.

Thanks again for the fast and detailed response.

[RohanNagar]

Hi @PascalSchumacher this improvement was made and released in version v1.4.1.

You can use it like the following:

EmailValidator validator = JMail.strictValidator().disallowObsoleteWhitespace();

validator.isValid("a@b .com"); // returns false

[RohanNagar]

Hi @PascalSchumacher! Thank you for the nice words 🙂

According to RFC 5322 and RFC 2822 those are valid (although unusual) email addresses.

Essentially, white-space is allowed between dot-separated parts of the local-part and the domain since RFC 822. This has been marked as obsolete in RFC 2822, which means that addresses should not be generated with whitespace, but they should be accepted as valid addresses by an email server, which is why JMail considers them as valid by default.

Appendix A.6.3 shows a valid example with the obsolete whitespace: jdoe@machine(comment). example

All that being said, in practice you may want to consider these addresses as invalid since the syntax is marked as obsolete. One way you could do that is by adding a rule to your validator that checks to make sure both the local-part and the domain do not contain whitespace:

JMail.strictValidator()
  .withRule(email -> !email.localPart().matches("\\S+") && !email.domain().matches("\\S+"))
  .isValid("a@b .com");

I think it would be a great idea for JMail to provide a rule which will do this kind of check so that you can add it like:

EmailValidator validator = JMail.strictValidator().disallowWhitespace();

I will keep this issue open as a to-do for that enhancement. Will probably not get around to it for another week or so.