You can configure your Platform.sh environments to send emails via an SMTP proxy.
Emails aren’t guaranteed to be deliverable and you can’t white-label them. The SMTP proxy is intended as a zero-configuration, best-effort service.
All non-production environments are limited to 12,000 email credits per calendar month.
Mail is enabled on your production environment by default. You can enable mail sending on your additional environments via the Console of CLI.
platform environment:info --environment ENVIRONMENT_NAME enable_smtp true
Please see our documentation on the detailed process as well as using external mail service on your project if the default option is not suitable to your needs.