How to use the nodemailer.sendmail function in nodemailer

function initMailer () {
    try {
        var settings = require('yaml').eval(require('fs').readFileSync(app.root + '/config/mailer.yml').toString('utf8'))[app.settings.env];
    } catch (e) {
        console.log('Could not init mailer extension, env-specific settings not found in config/mailer.yml');
        console.log('Error:', e.message);
        return;
    }
    if (!settings) {
        return;
    }
    exports.settings = settings;

    switch (settings.mailer) {
    case 'sendmail':
        nodemailer.sendmail = true;
        break;
    case 'smtp':
        nodemailer.SMTP = {
            host: settings.host || "localhost",
            port: settings.port || 25,
            use_authentication: settings.use_authentication || false,
            user: settings.user || '',
            pass: settings.pass || ''
        };
        break;
    }

    // read app/views/emails dir
    var emailsDir = app.root + '/app/views/emails';
    if (path.existsSync(emailsDir)) {
        fs.readdirSync(emailsDir).forEach(function (file) {

function ServerChannel (options, server, io) {
	
	this.options = options;
	this.server = server;
	this.io = io;
		
	this.name = options.name;
	
	if (options.mail) {
		nodemailer.sendmail = true;
		nodemailer.send_mail({sender: this.name, 
	        				  to: options.mail.to,
					          subject: options.mail.subject,
					          body: "MAIL. For now you cannot change this..."}, // TODO allow for custom body
			    function(error, success){
	            console.log("Message "+(success?"sent":"failed"));
	        });
	}
	
	this.nPlayers = options.nPlayers;
	
	
	this.adminChannel = options.admin;
	this.playerChannel = options.player;
	
	this.port = options.port;