我认为您正在寻找GmailApp.getMessagesForThreads().

I think you are looking for GmailApp.getMessagesForThreads().

function fetchEmails(){
  var sheet = SpreadsheetApp.getActiveSpreadsheet().getActiveSheet();
  var threads = GmailApp.search('label:searchedLabel');
  var messages = new Array();

  function Email(message){
    this.date = new Date(message.getDate());
    this.body = message.getBody();
  }

  var gmailMessages = GmailApp.getMessagesForThreads(threads);

  for(var i=0;i<thread.length;i++){
    var messagesForThread = gmailMessages[i];
    for(var j=0;j<messagesForThread.length;j++){
      if(messagesForThread[j].getFrom()=="firstName lastName <email@domain.com>"){
       var message = new Email(messagesForThread[j]);
       messages.push(message);
      }
    }
  }  
}

当然，您也可以写得更简洁一些(对不起，我无法提供一个机会来学习JavaScript的奇妙之处):

Of course you can also write this a little more concisely (sorry, I can't turn up an opportunity to educate about the wonders of JavaScript):

function fetchEmails(){
  var messages = Array.prototype.concat.apply([], GmailApp.getMessagesForThreads(
      GmailApp.search('label:searchedLabel')).map(function(messagesForThread) {
    return messagesForThread.filter(function(message) {
      return message.getFrom() == "firstName lastName <email@domain.com>";
    }).map(function(message) {
      return { date: new Date(message.getDate()), body: message.getBody() };
    });}));
}

这总共对Gmail进行了2次通话，因此速度很快.

This makes a grand total of 2 calls to Gmail, so it's going to be fast.

实际上，如果您按照上面的建议将"from"部分集成到搜索中，则只需要:

In fact, if you integrate the 'from' part into the search as was suggested above, all you need is:

function fetchEmails(){
  var messages = Array.prototype.concat.apply([], GmailApp.getMessagesForThreads(
    GmailApp.search('label:searchedLabel from:email@domain.com')).map(
      function(messagesForThread) {
        return messagesForThread.map(function(message) {
          return { date: new Date(message.getDate()), body: message.getBody() };
      });}));
}

最后，由于您实际上并不关心线程的结构，因此您可以在映射之前将数组连接起来，从而导致:

Finally, since you don't actually care about the thread structure, you can just concat the arrays before the map, which leads to this:

function fetchEmails(){
  var messages = GmailApp.getMessagesForThreads(
        GmailApp.search('label:searchedLabel from:email@domain.com'))
      .reduce(function(a, b){ return a.concat(b); })
      .map(function(message) {
         return { date: new Date(message.getDate()), body: message.getBody() }; 
      });
}

(我留在较早的示例中，以防您确实关心线程结构，而您只是给出一个最小的示例).

(I left in the earlier samples in case you do care about the thread structure and you were just giving a minimal example).