TEAMMATES supports third-party email services for sending emails. In most cases, you will need to register a domain name with the service and configure your DNS provider. Refer to each service's documentation for details.
Update the relevant values in build.properties after setting up your chosen service.
sendgrid.com — Create a free account and generate an API key.
mailgun.com — Create a free account and obtain your domain name and API key.
mailjet.com — Create a free account and obtain your API key and secret key.