This creates Labels on a schedule (when configured) for each new catch-all domain. For example, if you have [email protected] - it'll create a new label called "📬 flights"

Create-Labels-For-Catch-All.gs

// Configure this trigger to run often
// (*how* often depends on the desired response time *and* how willing you are to risk hitting Google Apps Script’s rate limits;
// 10 minutes is good enough for me generally)

var LABEL_DICT = {}
var EMAIL_WORKSPACE_DOMAIN = "" // do not include the @ sign, so for [email protected], put joebloggs.com

function getUserLabels() {
  GmailApp.getUserLabels().map((value) => {
    LABEL_DICT[value.getName().toString()] = value;
    return { "label": value, "name": value.getName() };
  });

}

function getLabelByName(name) {
  return LABEL_DICT.hasOwnProperty(name) ? LABEL_DICT[name] : undefined;
};

function createLabelIfNotExists(name) {
  var newLabel = null;
  var label = getLabelByName(name);
  if (!label) {
    newLabel = GmailApp.createLabel(name.toString());
    LABEL_DICT[name.toString()] = newLabel;
    label = newLabel;
  }
  return label;
};

function getLabelByEmailType(emailAddress) {
  if (!emailAddress) {
    return;
  }
  let emailLower = emailAddress.toString().toLowerCase();
  if (emailLower.toString().endsWith(EMAIL_WORKSPACE_DOMAIN)) {
    let futureLabel = emailLower.toString().split("@");
    return createLabelIfNotExists("📬 " + futureLabel[0]);
  };
};

function triggerScriptForEmail() {
  getUserLabels();
  let indicatorLabelString = "🆕";
  var LABEL_TO_REMOVE = LABEL_DICT[indicatorLabelString];
  var GET_THREADS_AT_TIME = 5;
  var threads = new Array();
  while (Array.isArray(threads)) {
    Logger.log(`Calling getUserLabelByName = ${indicatorLabelString}`);
    threads = GmailApp.getUserLabelByName(indicatorLabelString).getThreads(0, GET_THREADS_AT_TIME);
    Logger.log(`Thread length == ${threads.length}`);
    if (threads.length == 0) {
      Logger.log('All gone');
      return;
    }
    threads.forEach((thread) => {
      var messages = GmailApp.getMessagesForThread(thread);
      Logger.log(`${messages}`);
      var emailAddresses = messages.map((msg) => (msg.getTo ? [msg.getTo()] : [])).map((value) => value.toString().match(/([a-zA-Z0-9._-]+@[a-zA-Z0-9._-]+\.[a-zA-Z0-9_-]+)/gi));
      [...new Set(emailAddresses)].forEach((recipient) => {
        Logger.log(`Checking email address ${recipient}`);
        var labelToAttach = getLabelByEmailType(recipient);
        if (labelToAttach) {
          Logger.log(`Attaching label ${labelToAttach.getName()}`);
          labelToAttach.addToThread(thread);
        }

      });

      Logger.log(`Removing indicator label`);
      LABEL_TO_REMOVE.removeFromThread(thread);
      return null;
    })
  }

}
function doGet(e) {
  triggerScriptForEmail();
  return `OK`;
}