What I am sharing here is a really cool way to search email addresses. This trick will allow you to create a massive list of email addresses for marketing purpose. If you use it smartly, you can even get pre-made list of email addresses having thousands of email addresses.
All you need to do is, go to google and type this search string.
This will get you web results of notepad files of email addresses, specifically .txt files having email addresses ending on @gmail.com domain. You can try other file types and email providers such as;
You can try other variants as well, and can gather a great list of email addresses for marketing purpose. As this is a random list of email addresses, it would be your job to use these email addresses wisely so that you do not spam others.