nodejs: winston mail transport throw uncaughtException

In my nodejs express project, I am trying to set up emails on errors. using winston & winston-mail pkgs

I get the following error:

{
    "date": "Wed May 17 2017 12:36:54 GMT+0530 (IST)",
    "process": { "pid": 22443, "uid": 502, "gid": 20, "cwd": "/Users/shezad/workspace/goblin", "execPath": "/usr/local/Cellar/node/7.8.0/bin/node", "version": "v7.8.0", "argv": ["/usr/local/Cellar/node/7.8.0/bin/node", "/Users/shezad/workspace/goblin/server.js"], "memoryUsage": { "rss": 52514816, "heapTotal": 37646336, "heapUsed": 24661328, "external": 698215 } },
    "os": { "loadavg": [1.8125, 1.763671875, 1.7275390625], "uptime": 1126961 },
    "trace": [{
        "column": 13,
        "file": "/Users/shezad/workspace/goblin/node_modules/emailjs/smtp/error.js",
        "function": "module.exports",
        "line": 3,
        "method": "exports",
        "native": false
    }, {
        "column": 29,
        "file": "/Users/shezad/workspace/goblin/node_modules/emailjs/smtp/response.js",
        "function": "TLSSocket.error",
        "line": 26,
        "method": "error",
        "native": false
    }, {
        "column": 20,
        "file": "events.js",
        "function": "emitOne",
        "line": 101,
        "method": null,
        "native": false
    }, {
        "column": 7,
        "file": "events.js",
        "function": "TLSSocket.emit",
        "line": 191,
        "method": "emit",
        "native": false
    }, {
        "column": 8,
        "file": "net.js",
        "function": "emitErrorNT",
        "line": 1284,
        "method": null,
        "native": false
    }, {
        "column": 11,
        "file": "internal/process/next_tick.js",
        "function": "_combinedTickCallback",
        "line": 80,
        "method": null,
        "native": false
    }, {
        "column": 9,
        "file": "internal/process/next_tick.js",
        "function": "process._tickCallback",
        "line": 104,
        "method": "_tickCallback",
        "native": false
    }],
    "stack": ["Error: connection encountered an error",
        "    at module.exports (/Users/shezad/workspace/goblin/node_modules/emailjs/smtp/error.js:3:13)",
        "    at TLSSocket.error (/Users/shezad/workspace/goblin/node_modules/emailjs/smtp/response.js:26:29)",
        "    at emitOne (events.js:101:20)",
        "    at TLSSocket.emit (events.js:191:7)",
        "    at emitErrorNT (net.js:1284:8)",
        "    at _combinedTickCallback (internal/process/next_tick.js:80:11)",
        "    at process._tickCallback (internal/process/next_tick.js:104:9)"
    ],
    "level": "error",
    "message": "uncaughtException: connection encountered an error",
    "timestamp": "2017-05-17T07:06:54.696Z"
}

My logger.js file is like follow

var logger = new(winston.Logger)({

    transports: [
        new(winston.transports.Console)({colorize:true}),
        new(winston.transports.File)(config.logging.file_options),
        new(winston.transports.Mail)(config.logging.mail_options)
    ],
    exceptionHandlers: [
        new (winston.transports.Mail)(config.logging.mail_options)
    ]
});

Configuration for logging is as such

config.logging = {
    file_options: {
        name: 'app-log',
        filename: './logs/app.log',
        level: 'info',
        timestamp: true,
        colorize: true,
        handleExceptions: true,
        humanReadableUnhandledException: true,
        prettyPrint: true,
        json: true,
        maxsize: 512 * 1024
    },
    mail_options: {
        to: ['dummy@blackbuck.com'],
        from: '***@blackbuck.com',
        subject: format('[{0}]', config.stage_name.toUpperCase()) + '  : ',
        host: 'smtp.gmail.com',
        port: 587,
        username: '***@blackbuck.com',
        password: '******',
        ssl: true,
        prettyPrint: true,
    }
};

Can somebody please explain what this error is? and how to rectify it? Thanks in ad

via Crazyshezy