Auto Delete / Archive Emails in Gmail

autoDeleteGmail.js

/*
Original Sources: 
- https://pixelbakery.com/recipes/gmail-automatically-delete-or-archive-emails
- https://benbjurstrom.com/purge-email

v1.1
https://gist.github.com/zoidy

Auto-archive and delete Gmail messages based on a defined retention period. Functionality: 
- Uses Gmail labels to apply retention rules (archive or delete)
- Ability to customize retention period using the label text
- Handles large numbers of emails to process via (side steps the Google Apps Script execution limit by processing in batches).

To set up
1. Create a new Apps Script in your Google Drive and paste this code, then click the Save button
2. Under Services on the left hand side of the Apps Script editor, add Gmail
2. Run the install() function manually once to set up the permissions to gmail (select it from dropdown in the toolbar and click Run)
3. Add labels to Gmail messages to indicate what to archive and delete. The format is
    ARCHIVE_LABEL:#[d|w] A single message can have one ARCHIVE_LABEL and one DELETE_LABEL simultaneously. 

    Example: 
    Archive:2d = archive the message after 2 days
    Delete:12w = deletes the message after 12 weeks (84 days).
*/

ARCHIVE_LABEL = "Archive";      // label for messages that should be archived
DELETE_LABEL = "Delete";        // label for messages that should be deleted
DEFAULT_TIMEPERIOD_DAYS = 2.0;  //retention period if none is specified

// Maximum number of message threads to process per run. 
// It takes about 1.2 sec per email thread, so a 4 minute delay between processing runs
// when there are more than 175 items in a page is safe.
PAGE_SIZE = 175;
NEXT_RUN_DELAY = 4;

// How often to run the check, in hours. After installing the script, the interval can
// be changed either by running the uninstall function, changing the interval, and
// running the install function again, or by manually editing the existing trigger in the 
// AppsScript editor
PURGE_INTERVAL = 8;


// ####################################################################################

/**
 * Create a trigger that executes the purge function every day.
 * Execute this function to install the script.
 */
function install() {
  GmailApp.getUserLabels();
  ScriptApp.newTrigger('purge').timeBased().everyHours(PURGE_INTERVAL).create();
}

/**
 * Deletes all of the project's triggers
 * Execute this function to unintstall the script.
 */
function uninstall() {
  var triggers = ScriptApp.getProjectTriggers();
  for (var i = 0; i < triggers.length; i++) {
    ScriptApp.deleteTrigger(triggers[i]);
  }
}

/**
 * Create a trigger that executes the purgeMore function NEXT_RUN_DELAY minutes from now
 */
function setPurgeMoreTrigger(){
  ScriptApp.newTrigger('purgeMore').timeBased()
    .at(new Date((new Date()).getTime() + (1000 * 60 * NEXT_RUN_DELAY))).create();
}

/**
 * Deletes all triggers that call the purgeMore function.
 */
function removePurgeMoreTriggers(){
  var triggers = ScriptApp.getProjectTriggers();
  for (var i = 0; i < triggers.length; i++) {
    var trigger = triggers[i];
    if(trigger.getHandlerFunction() === 'purgeMore'){
      ScriptApp.deleteTrigger(trigger);
    }
  }
}

/**
 * Wrapper for the purge function
 */
function purgeMore() {
  purge();
}

function getDaysFromLabel(label) {
  /* 
  Expected format of label is LABEL:#T where LABEL is one of ARCHIVE_LABEL or DELETE_LABEL,
  # is a number, T is a time unit, currently only 'd' and 'w' is supported. Default is 'd'.

  Returns a number representing the number of days.
  */

  var timeunit = label.substring(label.length-1);
  var convertMult;
  var days;

  switch(timeunit) {
    case "d":
      // days
      convertMult = 1;
      break;
    case "w":
      // convert weeks to days
      convertMult = 7;
      break;
    default:
      return DEFAULT_TIMEPERIOD_DAYS;
  }

  days = parseFloat(label.substring(label.indexOf(":")+1,label.length-1)) * convertMult;
  if(isNaN(days))
    days = DEFAULT_TIMEPERIOD_DAYS;
  return days;
}

function process(action, labels) {
  /*
  Performs the action on the labels in the given array, extracting the retention period from the label.
  */

  console.log('Started ' + action + ' run.');

  var threadActions = [];
  switch(action) {
    //other actions are ["markRead", "markUnimportant"] but it slows things down
    case "autoArchive":
      threadActions = ["moveToArchive"];
      break;
    case "autoDelete":
      threadActions = ["moveToTrash"];
      break;
    default:
      Logger.log("Unrecognized action " + action);
      return;
  }
  
  for (var i = 0; i < labels.length; i++) {
    var labelToProcess = labels[i].getName();
    var retentiondays = getDaysFromLabel(labelToProcess);
    Logger.log("Processing " + labelToProcess + ", with retention " + retentiondays + " days.");

    var maxDate = new Date();
    maxDate.setDate(maxDate.getDate()-retentiondays);
    var totalthreads = GmailApp.getUserLabelByName(labelToProcess).getThreads().length;
    var processthreads = GmailApp.search('label:' + labelToProcess.replace(' ', '-') + ' older_than:' + retentiondays + 'd',
                                  0, PAGE_SIZE);

    if(processthreads.length > 0){
      Logger.log('Found ' + (totalthreads == 500 ? 'at least ' + totalthreads : totalthreads) + 
                 ' emails tagged with ' + labelToProcess + '. Processing ' + Math.min(processthreads.length, PAGE_SIZE));
      
      if (processthreads.length === PAGE_SIZE) {
        Logger.log('PAGE_SIZE exceeded. Processing will continue in ' + NEXT_RUN_DELAY + ' minutes.');
        setPurgeMoreTrigger();
      }

      var counter = 0;
      try {
        for(var j=0; j < processthreads.length; j++){
          var thread = processthreads[j];
          var threadDate = thread.getLastMessageDate();
          if (threadDate<maxDate){
            for(var k=0; k < threadActions.length; k++){
              thread[threadActions[k]]();
            }
            thread.removeLabel(labels[i]); //so processed items don't get reprocessed on future runs

            counter++;
            
            //uncomment for debugging but it slows things down
            //Logger.log('processed: ' + thread.getFirstMessageSubject() + ' [date: ' + threadDate + ']');            
          }
        }
        Logger.log('Successfully processed ' + counter + ' emails.');
      }
      catch(e){
        Logger.log('Error processing: ' + e);
      }
    }
    else
      Logger.log('Found ' + processthreads.length + ' emails marked for processing. Exiting.');
  }
}

function purge(){
  removePurgeMoreTriggers();

  var allLabels = GmailApp.getUserLabels();
  var archiveLabels = allLabels.filter((label) => {
    return label.getName().startsWith(ARCHIVE_LABEL);
  });
  var deleteLabels = allLabels.filter((label) => {
    return label.getName().startsWith(DELETE_LABEL);
  });
  
  process('autoArchive', archiveLabels);
  process('autoDelete', deleteLabels);
}

Thanks for this. I copied and pasted your code exactly, but am getting a 'Max Date is not defined' error, and cannot even install the script. I am in Australia, is this a time zone issue? As I understand it, the max date is defined at line 150 as 'var maxDate = new Date();' and 'new Date()' means 'now' - is that right? So, time zone should not matter.... Why else would max date be seen as not defined by the script? Any help would be really appreciated.

What line is that error being thrown for? If you are trying to install following the instructions (running the install() function), line 150 isn't even called