The email connector is built in to LoopBack, so you don't need to install it.

Creating an email data source

Create a new email data source with the data source generator:

$ slc loopback:datasource

When prompted, select Email as the connector.  This creates an entry in datasources.json like this (for example):

/server/datasources.json
 ...
 "myEmailDataSource": {
    "name": "myEmailDataSource",
    "connector": "mail"
  }
 ...

Configuring an email data source

Configure the email data source by editing /server/datasources.json (for example):

/server/datasources.json
{
    ...
    "myEmailDataSource": {
       "connector": "mail",
       "transports": [{
         "type": "smtp",
         "host": "smtp.private.com",
         "secure": false,
         "port": 587,
         "tls": {
           "rejectUnauthorized": false
         },
         "auth": {
           "user": "me@private.com",
           "pass": "password"
         }
       }]
    }
    ...
}

Connecting a model to the email data source

Then, connect models to the data source in /server/model-config.json as follows (for example):

/server/model-config.json
{
  ...
  "Email": {
    "dataSource": "myEmailDataSource",
  },
  ...
}