Mailtrap.io is a simple and very useful service for developing code that sends email. Set up a project inbox, tell your application to use smtp.mailtrap.io/port 2525 for mail transport and give it the username and password for your project inbox. Any emails your application sends (regardless of the outward address) are swallowed (no danger of spamming a real user with test emails) and emails can be reviewed in the project inbox. The free plan is generous enough to cover moderate usage.