What is the effect of drip marketing techniques on sales?

Sales usually go down when customers receive more than one email from a company, because they tend to delete them automatically.

Sales tend to go up when customers receive general emails since customers dislike targeted emails that indicate the company knows too much personal information.

Sales usually plummet because customers feel that they are interacting with an automated system rather than a real human being.

Sales go up dramatically when customers receive relevant, targeted emails rather than untargeted broadcast emails.