Aweber

Aweber is another industry-favourite for email marketing, particularly for creating autoresponders and pre-scheduled email sequences. It is compatible with other marketing programs you may encounter, including WordPress, Shopify, Heyo, Salesforce, Paypal, Facebook, and many others, making it easy to integrate your email sign-up form or list data as required. While Aweber is a paid solution, the monthly fee start at around $20/month, and provides industry-leading deliverability, tracking and email list management tools.

http://www.aweber.com