To avoid contacting the same prospect multiple time remember this:
- A prospect can only be in 1 campaign at a time. So don't worry, if you try to add a prospect that is already in a campaign, it just won't work.
- To select prospects that have never been contacted, use the prospects filter "Last sent email" -> "is unknown"
- When you open a prospect page and click on "Email" or "Campaign" you'll see a notice telling you'll be notified that the prospect has already been emailed.