Running a community has hidden costs all over the places and one of those costs that can quickly catch up to you is your mailing lists. I've user full featured services such as Mailchimp, Constant Contact and Campaign Manager as well as SMTP services like Mailjet, Sendgrid and Mandrill. While they all over great services, they all fall into two groups, ease of use at high price or robust API to build your own tools. There really isn't anything in the middle, but that appears to have changed with Sendy.
Sendy is a PHP web application similar to Wordpress that manages your newsletters and distrubutes them via Amazon's Simple Email Service (SES) on AWS. Just setup Sendy on a webserver of your choice, perhaps AWS, Digital Ocean, or anything that can be accessed via the web. Setup your AWS account for SES. And that is it. You now have the ability to send emails in large amounts at a cost effective manner.
Most email services pricing is based on two values. How many emails you plan on sending in a month and how large is your list. Some will even charge you based on both. Where Sendy changes that is you own the software. It is a site license. So all you are paying for after buying the software is the emails you send via SES. SES is also cheap. Not just cheap, but dirt cheap. If you have a list of 50,000 users and want to send one email a month that would be around $300 a month using some of the full featured tools and around $100 a month with the SMTP tools. With Sendy, that campaign to 50,000 users would cost you $5.
At that price there has to be some tricks or hidden cost, but really there isn't. The only issue in my research has been that SES is a fairly new service. With any new services you are going to have hickups, which they seem to be resolving. The other is the email limits via SES upon starting, which is 10,000 email sends every 24 hours at a rate of 5 emails per second. So your 50,000 emails would be done in a little under three hours.
Sendy appears to be a great option for someone wanting to have a newsletter and not worry about the cost creeping up on you.