qregexpvalidator qlineedit email address
QRegExp mailREX("\\b[A-Z0-9._%+-]+@[A-Z0-9.-]+\\.[A-Z]{2,4}\\b");
mailREX.setCaseSensitivity(Qt::CaseInsensitive);
mailREX.setPatternSyntax(QRegExp::RegExp);
qDebug() << mailREX.exactMatch("[email protected]");