MX Lookup

The tool reads the MX records of a domain and checks each mail server separately: whether its hostname resolves to an address, whether the record holds a bare IP or a CNAME alias, and whether it points into a private network. Records with these errors look normal in a list, but mail never reaches the server.

When MX records are missing, mail goes to the domain's own address, as the standard prescribes. A record of "0 ." means the domain explicitly refuses mail. The tool names both cases plainly, and it recognizes the mail provider behind the server names: Yandex 360, VK WorkSpace, Google Workspace, Microsoft 365, and others.

Reverse names and spam lists

Every mail server address is checked for a reverse name (PTR) and whether that name points back to the same address. Receiving mail does not require this, but if the server also sends mail, Gmail and other receivers demand the matching pair.

IPv4 addresses are checked against the Spamhaus, Barracuda, and DroneBL lists. All records of a domain, together with SPF and DMARC, are shown by the DNS records check.