How to automate different replies regarding the sender or type of answer?

1. Open an existing thread. Or write and send a new email to someone, then open that new message in your Sent Mail folder. 2. Open a reply to the conversation and write your follow-up note. 3. When you finish writing your reply, click the Send Later button, and then check the “Only if nobody replies” checkbox before scheduling your message. That’s it! If you don’t get a reply to the thread before the scheduled time, Boomerang will send your message automatically.