How to search for email address which sends back automated response?

I would like to test the functionality of a mailbox. I need an email address to which I send an email and then I can verify the response. So it should be an email address which responses automatically with an email in like 1 minute. I was trying to google it many ways but cannot find any, the results are always only for "how to create automatic response" but that is not what I need. Anyone has any idea how to find such a provider? Or you know one? Thanks in advance