When you send out your campaign, you might think that you send it, promote your business, and then your clients will contact you to buy from you. But in reality, it does not work that way, you should actually try to interact with your clients, and have them click on a button to reply to you, no matter how far they are from you.
One of the most important things in Email Marketing is to get permission from the recipients to receive your newsletters. Without obtaining this permission you may be considered a spammer and be blocked by email providers. By the contrary, by obtaining the permission of your clients, you are creating a relationship with them so that your business can grow.