A follow-up email is an email that is sent after the initial contact with a view to develop subscriber-engagement.  It is done with the aim of building relationship with the lead.  Follow-up email is normally sent after 2 or 3 days of the first interaction with the subscriber.  

The primary benefit of follow-up emails is that they tend to build the interest of the prospect in your product or service.  Follow-up email will help you to hear more from your prospect.  A follow-up email can end in a sale much to your delight and satisfaction.  

Follow-up email if composed well can get you surprising results as well.  By reminding your prospect about the pros and cons of your product or service, you are only making your prospects to have a try on your product, by leading them to a Webinar, or making them go through an inforgraphic, or getting them answer a survey. 

Follow-up emails can also be a series of emails so you can be in touch with your prospects in the long run.  It is better to adhere to a limited number of follow-up emails so your credibility remains in tact.  A powerful e-commerce email marketing solution will guide you precisely while sending follow-up emails to your prospects.