@SuppressWarnings("unchecked")
	public T protocol(String protocol) {
		ensureNotStarted();
		this.protocol = protocol;
		return (T) this;
	}
Base class support for both "mail" and "imap".

@author Eric Bottard
spring-xd-test-fixtures/src/main/java/org/springframework/xd/test/fixtures/AbstractMailSource.java