I've been on multiple email broadcast providers over the years, and have a very large list that I rely on as central to my business. Other providers have let me down in multiple ways, but since making the switch to Convertkit (recently renamed Seva), I've never looked back!
The backend interface is straightforward and pleasant to use (I would dread logging into a competitor that shall remain nameless), emails make it through totally fine even when you are sending to 6-digits of subscribers, lots of really cool features like per-location filtering, if-else-based tagging within emails so you can write a single email that's tweaked rather than multiple, visual automation, great analytics, fast loading site, robust rules with tagging and segmentation to give you interesting ways to send very tailored emails, and tech support that are available 24-hours who reply very quickly.
When you need to send a broadcast to so many people, you want to do it right. The company has a great family feel to it, and I actually get genuinely excited every summer when they announce a ton of new features and improvements. Whenever I try to push the technical limits of their new additions, they are very good at working with my many requests to make sure everything is seamless.
I wasn't prompted to write this review - As well as being one of their bigger customers, I'm also one of their bigger fans. :D
Forward Thinking Email Marketing Software For Savvy Entrepreneurs