function MailURLMayBeInvalid(const s: string): Boolean;
var
  i: Integer;
  c: string;
begin // ' ', ä, ö, ü, ß, [, ], (, ), : in EMail-Address
  Result := (Trim(s) = '') or (Pos(' ', AnsiLowerCase(s)) > 0) or
    (Pos('ä', AnsiLowerCase(s)) > 0) or (Pos('ö', AnsiLowerCase(s)) > 0) or
    (Pos('ü', AnsiLowerCase(s)) > 0) or (Pos('ß', AnsiLowerCase(s)) > 0) or
    (Pos('[', AnsiLowerCase(s)) > 0) or (Pos(']', AnsiLowerCase(s)) > 0) or
    (Pos('(', AnsiLowerCase(s)) > 0) or (Pos(')', AnsiLowerCase(s)) > 0) or
    (Pos(':', AnsiLowerCase(s)) > 0);
  if Result then Exit; // @ not in EMail-Address;
  i      := Pos('@', s);
  Result := (i = 0) or (i = 1) or (i = Length(s));
  if Result then Exit;
  Result := (Pos('@', Copy(s, i + 1, Length(s) - 1)) > 0);
  if Result then Exit; // Domain < = 1
  c      := Copy(s, i + 1, Length(s));
  Result := Length(c) <= 1;
  if Result then Exit;
  i      := Pos('.', c);
  Result := (i = 0) or (i = 1) or (i = Length(c));
end;