I'd like to second SendGrid. In my previous job, we were using MailChimp until they decided that for some reason some of the communication (the campaings that

I'd like to second SendGrid. In my previous job, we were using MailChimp until they decided that for some reason some of the communication (the campaings that are created manually via their interface) with our clients was spam. They did not give us any warning but one day they blocked everything, including the API (mandrillapp), which our system was using to send email as part of our process. We moved our mail lists to SendGrid while decoupling the API, using AWS SNS for that. I hate companies that treat you as if they were doing you a favour (we were paying customers, and worse that they don't sit down and talk to understand what is the situation. No business sense at all.