The subject of this article is something I want to separate, email for marketing and phone for sales. If you are looking to have some sales on your website, or build respect with your users, use email. But if you want to sell to a specific person, the telephone is the best option.
Why phone?
First of all, the telephone can help your customers to get answers in a faster way. Sure you can answer these questions by email, but this will take a little longer. Send an email, they get it, maybe they'll reply to it, or maybe they won't. On the phone the responses are instantaneous, you speak and the customer responds, and vice versa.
Perhaps you have been in situations where you are selling, and you send an email with little information. So you wait a day, or maybe a whole week. Then the client send you a question back, to which you respond after a day or a week. On the phone, this does not happen because they can clarify everything in the fastest way.
Email is a supplement
Many salespeople train to use their email as a supplement to your sales. You can use your email to do a little outreach. But primarily they use it as a reminder to their customers and then switch to using the phone for the sale.
One point for using this is a tracker for emails like HubSpot is, so you can see if your customer has opened your mail. And when you open it, wait 5 minutes and give him a call so you can have a conversation with him with the topic of the sale on your mind.