I’m using mailcow with nextcloud. I can connect my email account in nextcloud as a sender. Here I notice after setting up the server address, port and an existing email address, I can leave the SMTP username and password blank sending emails.
But I am assuming that I am supposed to be authenticated? If it’s not necessary, does it mean that anyone knows my mail server address, port and an email address under my domain is able to send emails using SMTP?
I don’t want my server to become a spam server. Thanks very much if someone can answer this.