Custom Email address validation using JavaScript in ASP.Net

I entered email id as Dmwaura@packwood.africa and i got error as "incorrect email address".What changes is needed so that it will accept that email id?

javascript code:

 var email = document.getElementById("<%=txtEmail.ClientID%>").value;
 var emailPat = /^[a-zA-Z0-9._-]+@[a-zA-Z0-9.-]+\.[a-zA-Z]{2,4}$/;
 var matchArray = email.match(emailPat);
  if (matchArray == null) 
  {
              alert("Your email address seems incorrect. Please try again");
              document.getElementById("<%=txtEmail.ClientID%>").focus();
              return false;
  }

Source code:

 <td align="left">
      <asp:TextBox ID="txtEmail" runat="server" Width="196px" Height="19px"></asp:TextBox>
  </td>