This Google App script parse gmail messages with specific label and put them a spreadsheet in your drive. I am using Gmail filter to put label to these message and remove this label after parsing to only parse new message on every turn.

GmailParser.gs

function searchMessageWithLabel() {
  var labelName = "My Label";
  var response = GmailApp.search("label:" + labelName);
  var label = GmailApp.getUserLabelByName(labelName);
  if (response.length == 0) {
    Logger.log("No messages available.");
  } else {
    Logger.log("Messages");
    for(var i = 0; i < response.length; i++) {
      var messages = response[i].getMessages();
      var firstMessage = messages[0];
      Logger.log("%s - %s", i, firstMessage.getFrom());
      sendDataToSpreadSheet(firstMessage.getFrom(), firstMessage.getDate(), firstMessage.getSubject(), firstMessage.getPlainBody());
      response[i].removeLabel(label).refresh();
    }
  }
}

function sendDataToSpreadSheet(from, date, subject, message) {
  var spreadSheetName = "My Sheet"
  var sheet
  var files = DriveApp.getFilesByName(spreadSheetName);
  if (files.hasNext()) {
    var spreadsheets = SpreadsheetApp.open(files.next());
    sheet = spreadsheets.getSheets()[0];
    
  } else {
    sheet = SpreadsheetApp.create(spreadSheetName);
  }
  sheet.appendRow([from, date, subject, message]);
  SpreadsheetApp.flush();
}

<?xml version='1.0' encoding='UTF-8'?><feed xmlns='http://www.w3.org/2005/Atom' xmlns:apps='http://schemas.google.com/apps/2006'>
	<title>Mail Filters</title>
	<id>tag:mail.google.com,2008:filters:1493894907273</id>
	<updated>2017-05-04T10:49:30Z</updated>
	<author>
		<name>Amit Kumar Swami</name>
		<email>amit@abc.com</email>
	</author>
	<entry>
		<category term='filter'></category>
		<title>Mail Filter</title>
		<id>tag:mail.google.com,2008:filter:1493894907273</id>
		<updated>2017-05-04T10:49:30Z</updated>
		<content></content>
		<apps:property name='from' value='*@abc.com'/>
		<apps:property name='to' value='*@abc.com'/>
		<apps:property name='hasTheWord' value='wfh OR leave OR WFH/Leave OR Leave OR WFH'/>
		<apps:property name='label' value='WFH'/>
		<apps:property name='shouldStar' value='false'/>
		<apps:property name='sizeOperator' value='s_sl'/>
		<apps:property name='sizeUnit' value='s_smb'/>
	</entry>
</feed>

Filter for gmail to put labels to specific messages.