I doubt you really want space,
I think you want to fix width of that coloumn.
<asp:boundfield headertext="Email" datafield="Email" xmlns:asp="#unknown">ItemStyle-Width="75" />
</asp:boundfield>
or if you really want space then
onRowBound event of gridview
protected void rowbound(object sender, GridViewRowEventArgs e)
{
GridViewRow row = e.Row;
string s = row.Cells[5].Text;
s = s.PadLeft(50, ' ');
row.Cells[5].Text=s;
}