code: public void releaseMailAccountForThread(final String accountReservationKey) {
  		lock.lock();
  		try {
  			MailAccount mailAccount = lookupUsedMailAccountForCurrentThread(accountReservationKey);
  			releaseMailAccountForThread(mailAccount);
  		} finally {
  			lock.unlock();
  		}
  	}
docs: Releases the mail account reserved under the specified reservation key for the current thread
  so it can be reused by another threads. Threads blocking on an attempt to reserved an account
  are notified.
  
  @param accountReservationKey
  the reservation key