Gmail で特定ラベルの大量なメールを削除するバッチ関数（どっかで拾ったもの）

batch-delete-email.gs

function batchDeleteEmail() {
  var loopNumber = 50
  var batchSize = 100 // Process up to 100 threads at once
  var searchSize = 400 // Limit search result to a max of 400 threads. Use this if you encounter the "Exceeded maximum execution time" error
  
  for (i = 0; i < loopNumber; i += 1) {
    var threads = GmailApp.search('label:XXXX', 0, searchSize);
    for (j = 0; j < threads.length; j += batchSize) {
     GmailApp.moveThreadsToTrash(threads.slice(j, j + batchSize));
    }
  }
}