[whycombagator]

For SES there is also this repo from freecodecamp[0]. And also Moon Mail[1][2]. I am sure there are more too.

For a paid, non SES, option I personally like SendGrid[3] more than Mailgun.

[0] https://github.com/freeCodeCamp/mail-for-good

[1] https://moonmail.io/

[2] https://github.com/MoonMail/MoonMail

[3] https://sendgrid.com/