2 ways:
A.
1. Make the final channel before the FTP adapter a <publish-subscribe-channel />
2. Subscribe the FTP adapter and, say, a <service-activator /> to the channel. Put an "order" attribute on each (1 on FTP, 2 on the service activator).
B.
Instead of a pub-sub channel, use a <recipient-list-router/> (with the ignore-send-failures attribute set to its default 'false').
In both cases, the message will be sent to the second subscriber only if the send to FTP is successful.
Gary P. Russell
Spring Integration Team
SpringSource, a division of VMware