if (toEntityContainer == null) {
toEntityContainer = toPostbox.getNext();
}
// Compare the two sources.
comparisonResult = comparator.compare(fromEntityContainer, toEntityContainer);
if (comparisonResult < 0) {
// The from entity doesn't exist on the to source therefore
// has been deleted. We don't know when the entity was
// deleted so set the delete time to the current time.