Packaging SMTP(send only) APIs to a choosable option is the goal here, then to have a tiny server that picks 1 provider and serves as HTTP endpoint so the other microservices that belong to you can make email requests.
- Brevo (highly recommended)
- Resend
- Postmark
- Mailchimp
- Mailtrap
- Mailjet
- Mailgun
- Sendgrid (avoid them if you can)
Note: Anything that only uses oauth2 like zoho does will not be implemented here for foreseeable future