function auto_delete_mails() {
var label = GmailApp.getUserLabelByName("Delete Me");
if(label == null){
GmailApp.createLabel('Delete Me');
}
else{
var delayDays = 2 // Enter # of days before messages are moved to trash
var maxDate = new Date();
maxDate.setDate(maxDate.getDate()-delayDays);
var threads = label.getThreads();
for (var i = 0; i < threads.length; i++) {
if (threads[i].getLastMessageDate()<maxDate){
threads[i].moveToTrash();
}
}
}
}