I saw it on zapier and tested it.
When receives an email an url is extracted and a webhook request is sent which verifies the email from which the email is received.
Is it possible in n8n.io
There is the “EmailReadImap Node” which can listen for new emails and trigger the workflow whenever one gets received.
It will then give access to the sender-address and the content. That can then be used for whatever. Like sending it with an HTTP-Request Node somewhere to verify and then depending on that call another URL, send an email, Slack message, …