Some servers expose custom port and hostname options through environment variables. To support these, create a new configuration file `config/local.js`:
```
module.exports = {
www: {
port: process.env.OPENSHIFT_NODEJS_PORT,
host: process.env.OPENSHIFT_NODEJS_IP
}
};
```
Mailtrain uses [node-config](https://github.com/lorenwest/node-config) for configuration management and thus the config files are loaded in the following order:
1. default.toml
2. {NODE_ENV}.toml (eg. development.toml or production.toml)
* **SparkPost** – use `http://domain/webhooks/sparkpost` as the webhook URL for bounces and complaints ([instructions](https://github.com/andris9/mailtrain/wiki/Setting-up-Webhooks-for-SparkPost))
* **SendGrid** – use `http://domain/webhooks/sendgrid` as the webhook URL for bounces and complaints ([instructions](https://github.com/andris9/mailtrain/wiki/Setting-up-Webhooks-for-SendGrid))
* **Mailgun** – use `http://domain/webhooks/mailgun` as the webhook URL for bounces and complaints ([instructions](https://github.com/andris9/mailtrain/wiki/Setting-up-Webhooks-for-Mailgun))
Additionally Mailtrain (v1.1+) is able to use VERP-based bounce handling. This would require to have a compatible SMTP relay (the services mentioned above strip out or block VERP addresses in the SMTP envelope) and you also need to set up special MX DNS name that points to your Mailtrain installation server.