NextAuth.js wants you to use an SMTP connection string when using their “Email” authentication provider.
It took me a while to figure out how to get an SMTP connection string for Amazon Simple Email Service, but once I did I wrote this quick guide: How to send email through Amazon SES with SMTP.
Follow that guide to set up NextAuth.js like this:
providers: [
Providers.Email({
server: "smtp://username:password@email-smtp.us-east-1.amazonaws.com:587",
from: "system@example.com", // A domain you've set up in Amazon SES' console
}),
];