What is the drip for?

It spreads the sending over any period you choose, from 1 to 60 days instead of sending everything at once. The option reads “0 days” when you want it all right away.

On a long list, the drip avoids sending everything on the same day. On a new site, it matches the pace at which pages actually go live.

Credits, though, are charged when the batch is created, not day by day.