I researched the 12 best email marketing tools a few months ago.
I'm using MailerLite because they offer a very generous free tier with 1,000 subscribers and 12,000 emails/month.
Also, you can set up email automation with custom workflows. I haven't found this feature in a free tier anywhere else.
For transactional emails, I use MailerSend (free tier) and Sendgrid.
@jonathanm yeah it's ok, my problem is I have a particular requirement that has had an issue open in Github for months without being resolved. We'll have to switch eventually if there is no resolution. But at least the emails don't go to spam :D!
@rosie_higgins_grapevine wow thanks for your feedback, that's definitely good to know for the future! I read that their service quality went down as they started having big clients. Will keep that in mind when our requirements will change :)
As for dynamic/responsive emails, my team and I are using open-source MJML templates. You can check it out at https://mjml.io/ and https://github.com/mjmlio/mjml
Having that set it doesn't really matter which email service provider platform we use to send them as the results are always astonishing.
MJML has been built by Mailjet and released publicly a few years ago. These templates work fine with Mailjet, SendGrid, SendInBlue and MailGun.