Strange Remarks validation error

I tracked down the error to this function. Any of the words (or words that contain the following) in injection_strings will give an invalid remarks popup and not allow the message to be sent:

function is_valid_remarks(a)
{
  a=jQuery.trim(a);
  injection_strings="apparently-to cc bcc boundary charset content-disposition content-type content-transfer-encoding errors-to in-reply-to message-id mime-version multipart/mixed multipart/alternative multipart/related reply-to x-mailer x-sender x-uidl".split(" ");
  for(i=0; i<injection_strings.length; i++)
    if( -1 != a.indexOf(injection_strings[i]))
      return!1;
    return!0
}