Maybe it would be better to replace Zend_Validate_Hostname with a custom validator and library, eg Piwik\Intl\DomainName? It could ship with a list of TLDs and IDNs but also have a way to download/use an out-of-band update.

Hi @robocoder
Thanks for the PR 👍 Noticed that the integration test which checks against many TLDs is now failing in: https://travis-ci.org/matomo-org/matomo/jobs/340708272

1) Piwik\Tests\Integration\EmailValidatorTest::test_allCurrentTlds
preg_match(): Compilation failed: regular expression is too large at offset 156184
/home/travis/build/matomo-org/matomo/libs/Zend/Validate/Hostname.php:2358
/home/travis/build/matomo-org/matomo/libs/Zend/Validate/EmailAddress.php:487
/home/travis/build/matomo-org/matomo/libs/Zend/Validate/EmailAddress.php:546
/home/travis/build/matomo-org/matomo/core/Piwik.php:575
/home/travis/build/matomo-org/matomo/tests/PHPUnit/Integration/EmailValidatorTest.php:21
/home/travis/build/matomo-org/matomo/tests/PHPUnit/Integration/EmailValidatorTest.php:66

Would you be able to update this integration test so it passes again?

I'll look at it later this evening.

The regex pattern buffer max length is determined by a compile-time setting when building php. Since this can vary between platforms, I arbitrarily used a cutoff of 256.

Please remove the Pull Request WIP tag.