public void recipient(String recipientString) throws RejectException {
try {
Recipient recipient = convertToRecipient(recipientString);
RecipientContext recipientContext =
new RecipientContext(mailTransaction, recipient);
FilterReply filterReply =
filterChain.getHead().verifyRecipient(recipientContext);
if (filterReply == FilterReply.NEUTRAL) {
if (!recipientContext.isDestinationAssigned()
|| (recipientContext.getDestination() instanceof UnknownRecipientDestination))
throw new UnknownUserException(recipientContext.recipient);