It’s the email address that is configured at notification email in your Discourse settings and I assume that you’ve added your email address there.
I have noreply@mydomain.com configured as notification email address, indicating that it’s not intended for bidirectional communication.
Another option would be to enable reply by email, which essentially creates a way of posting on Discourse via email. However, this involves a little bit of configuration and setting up a dedicated email account handling the replies.