Regex email validation cross-platform behavior problem

Question

Pattern: ^(?=.{6,265}$)(-|_)*[^\\W_](?:[+\\w.-]*[^\\W_])*(-|_|\\.)*@(?:\\[[0-9]{1,3}\\.[0-9]{1,3}\\.[0-9]{1,3}\\.|(?:[\\w-]+\\.)+)(?:[a-zA-Z]{2,13}|[0-9]{1,3})\\]?$