// Helper function for converting array to coma separated list
function convertToComaSeparatedList (arrayList) {

	if ( arrayList == null || arrayList.length == 0) {
		return null
	}

	var outStr = "";
	for (var i=0; i < arrayList.length; i++) {
		outStr += arrayList[i] + ",";
	}
	if (outStr.length > 0){
		outStr = outStr.substring(0, (outStr.length - 1));
	}
	return outStr;
}

var message = new EmailMessage();

// Override default settings if and only if input parameter is set
if ( smtpHost != null && smtpHost.length > 0 ){
	message.smtpHost = smtpHost;
}
if ( smtpPort != null && smtpPort > 0 ){
	message.smtpPort = smtpPort;
}
if ( username !=null && username.length > 0){
	message.username = username;
}
if ( password != null && password.length > 0){
	message.password = password;
}
if ( fromName != null && fromName.length > 0){
	message.fromName = fromName;
}
if ( fromAddress != null && fromAddress.length > 0){
	message.fromAddress = fromAddress;
}

// Build Address Lists
message.toAddress = convertToComaSeparatedList(toAddressList);
message.ccAddress = convertToComaSeparatedList(ccList);
message.bccAddress = convertToComaSeparatedList(bccList);

// Set subject
message.subject = subject;

// Add text part of the email
message.addMimePart(content,"text/html; charset=UTF-8");

// Add attachment
message.addMimePart(attachment, attachment.mimeType);

// Send message
message.sendMessage();