What is the best app to design and send customized emails to customers on your email marketing list?

In my opinion, Mailchimp is the best email marketing tool. You can create email sequences that send out automatically when a customer performs a certain action. You can also customize the email to include the customer's name.

I recommend Campaign Monitor. You can use it to customize emails with the first name of the customer, it is easy to set-up and very affordable for small email marketing lists.

MailChimp is definitely the best bang for your buck. I have been using it for years and absolutely love it!