code: public void setProxyuser(String proxyuser) throws ApplicationException {
  	try {
  	    smtp.getProxyData().setUsername(proxyuser);
  	}
  	catch (Exception e) {
  	    throw new ApplicationException("attribute [proxyuser] of the tag [mail] is invalid", e.getMessage());
  	}
      }
docs: set the value username When required by a proxy server, a valid username.
  
  @param proxyuser value to set
  @throws ApplicationException