The validemail extension extends TYPO3's standard email validation with an improved TLD validation. It adds a check for the domain, so that at least one dot is present after the @-sign.

When doing a manual test, the browser validation will prevent you from submitting the form, if the email address is invalid.

Bots just send the form data to the action URL of the form tag, and then the \TYPO3\CMS\Core\Utility\GeneralUtility::validEmail method is usually used to validate the email address. This method uses egulias/email-validator which does not check if the domain contains a dot.

Do not install this package if you send emails to local addresses or in an intranet environment that do not have a dot in the domain part.

If you want to test this behavior yourself, deactivate JavaScript in your browser, which will also disable the browser validation. Then submit your form with something like "test@example" - this will be accepted by the validEmail check without this extension.

See these issues for additional information:

• https://forge.typo3.org/issues/102629
• egulias/EmailValidator#359

composer require andreaskiessling/validemail

Running the unit tests with https://github.com/nektos/act and g1a/composer-test-scenarios locally:

act --matrix php-version:7.4 --action-offline-mode
act --matrix php-version:8.1 --action-offline-mode
act --matrix php-version:8.2 --action-offline-mode
act --matrix php-version:8.3 --action-offline-mode
act --matrix php-version:8.4 --action-offline-mode

This extension will hopefully be obsolete once egulias/EmailValidator#359 is solved.