FILTER_VALIDATE_EMAIL disallows a number of potentially existing email addresses.
This includes valid examples such as:
- mesut@özil.de (valid IMA)
- mesut.özil@arsenal.com (valid IMA)
- инфо@кто.рф (valid IMA)
- admin@localhost (locally valid)
- admin@something (locally valid)
The OR referred to an address formally incorrect per RFC but obviously existing:
- test.@aon.at
Many more complex syntaxes are allowed per RFC though usually not used or accepted.
Original report
Just tried to create a user that has an email with a dot at the end, like test.@aon.at - which is a valid email address. I know two people who have such an address.
Drupal refuses to create that user and says that the email is not valid.
The code that verifies the email must have an issue here.