SuperTokens is an open source authentication solution offering features like: Different types of login: Email / password, Passwordless (OTP or Magic link based).

SuperTokens.com

How can I customize the OTP email that is sent with passwordless login?

See this section: https://supertokens.com/docs/passwordless/email-delivery/about

I have set this up. But I am getting connection refused from the SMTP server

make sure the smtp settings are right. You can reach out to godaddy for help with this.

We raised a request with SES for SMTP access since GoDaddy was not working correctly with SuperTokens

They wanted to know how you manage bounces, complaints, and unsubscribe requests. Is there any documentation for the same?

bounces are ignored, could you elaborate on compliants? Also, there is no unsubscribe here cause we sned only transactional emails and no marketing emials, so it makes no sense to have an unsubscribe button.

Ok. Thank you for the response I will check with AWS support