Google app script to aggregate email sender domains by count for finding who sends you the most email.

aggregate_senders.gs

/**
 * A Google app script that gathers threads from your inbox and sorts the
 * sender domains by quantity of emails, then outputs to a spreadsheet.
 */

/** Given a sender, return just the domain of the email address. */
function getSenderDomain(sender) {
  // parse from '"My Name" <myemail@domain.com>'
  var regex = RegExp("(?:<.*@)([^>]*)");
  var matches = regex.exec(sender);
  if (matches)
  {
    return matches[1];
  }

  // try simpler regex, just 'myemail@domain.com'
  var regex2 = RegExp("(?:@)([^>]*)");
  matches = regex2.exec(sender);
  if (matches)
  {
    return matches[1];
  }

  Logger.log("Error: Failed to parse domain from sender: " + sender);
  return sender;
}

/** Return a sorted array of tuples containing [(count, sender), ...] */
function sortDomainCounts(countByDomain) {
  var keys = Object.keys(countByDomain);
  var values = [];
  var tuples = [];
  keys.forEach((domain) => {
    values.push(countByDomain[domain]);
    tuples.push([countByDomain[domain], domain]);
  });

  return tuples.sort((a, b) => b[0] - a[0]);
}

function myFunction() {
  var startThread = 0;
  var stepSize = 100;
  var endThread = 2000;

  var countsByDomain = {};

  while(startThread <= endThread) {
    var threads = GmailApp.getInboxThreads(startThread, Math.min(stepSize, endThread - startThread + 1));
    if (threads.length == 0) {
      break;
    }
    for (var idx = 0; idx < threads.length; idx++) {
      var sender = threads[idx].getMessages()[0].getFrom();
      var domain = getSenderDomain(sender);
      if (!countsByDomain[domain])
      {
        countsByDomain[domain] = 0;
      }
      countsByDomain[domain] += 1;
    }
    startThread += threads.length;
    Logger.log("Processing " + startThread);
  }

  // collect into array of tuples for sorting
  var sortedDomains = sortDomainCounts(countsByDomain);
  // output to doc
  var docName = "Email Stats [" + 0 + "-" + endThread + "]";
  var outputRange = SpreadsheetApp.create(docName).getSheets()[0].getRange(1, 1, sortedDomains.length, 2);
  outputRange.setValues(sortedDomains);

  Logger.log("Finished!");
}