I use a docker image called maildev - it simulates a SMTP server and I can view all sent emails locally in a web UI to make sure the format looks visually OK

EDIT: Here's the docker-compose.yml file I use for development on most of my apps. Make sure to leave the MAILDEV_IP environment variable as it is there, it's important to make sure the healthcheck runs properly:

services:
  db:
    image: postgres:16.3
    restart: always
    environment:
      - POSTGRES_DB=unblock_domains
      - POSTGRES_USER=postgres
      - POSTGRES_PASSWORD=password
    ports:
      - 5432:5432
  smtp:
    image: maildev/maildev:2.1.0
    restart: always
    environment:
      - MAILDEV_INCOMING_USER=smtp
      - MAILDEV_INCOMING_PASS=password
      - "MAILDEV_IP=::"
    ports:
      - 1080:1080
      - 1025:1025

In terms of validating that emails will be sent at the right time to the right person - this is where automated tests are super useful.

Then I just let it rip!