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;  
 
  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;

  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;