Unify the email validation of UserUtil::isValidEmail() and Mailbox::__construct()
Unify the email validation of UserUtil::isValidEmail() and Mailbox::__construct()

WoltLab/WCF,WoltLab/WCF,SoftCreatR/WCF,SoftCreatR/WCF,SoftCreatR/WCF,WoltLab/WCF,SoftCreatR/WCF,WoltLab/WCF