A DANE TLSA record for SMTP services should be located at
_25._tcp.[mx-host], where mx-host is the hostname of the inbound SMTP (MX) service.
Note: submit the MX host name (not the domain name) in the input box.
This tool verifies the correctness of the syntax of the TLSA record, it does not (yet) perform matching of the TLSA records against the SMTP server certificate.