I had the same issue with SMTP and how to configure it. I can confirm that most likely it is an issue with how you have configured your SMTP and FusionAuth.
BTW I have created this monorepo which utilizes FusionAuth, Docker, mailcatcher, NestJS, and NextJS. Check how I wrote fusionauth.docker-compose.yml and how terraform is configuring FusionAuth. I also jot down here and there some infos about them, so if you like you can definitely read README.md files.
I also appreciate it if you give it a star on GitHub.