Sigh. We've been through all this with you before in great detail. https://groups.google.com/g/prometheus-users/c/LZbihDncIig/m/cqAA-UtdAQAJ
Port 587 is SMTP submission, and it does not perform TLS on connection. Try "telnet dns 587" and you'll see it responds in plain text, which is just what the error message told you: "tls: first record does not look like a TLS handshake" To get it to do TLS, you need to send the "starttls" command before starting the TLS negotiation, like this example <https://github.com/prometheus/blackbox_exporter/blob/master/example.yml#L91-L104> and in the thread linked above. -- You received this message because you are subscribed to the Google Groups "Prometheus Users" group. To unsubscribe from this group and stop receiving emails from it, send an email to prometheus-users+unsubscr...@googlegroups.com. To view this discussion on the web visit https://groups.google.com/d/msgid/prometheus-users/351bd2be-8e6c-451f-bea6-8c9e7b31639an%40googlegroups.com.
