SPF record

An SPF record is a type of DNS record. It specifies the mail servers that are allowed to send email on behalf of a domain and prevents spam from being sent with forged sender addresses belonging to a specific domain.

The recipient can check the SPF record to determine whether the message was sent from the domain or sent by an authorized mail server.

The principle of SPF technology is as follows:

SPF allows the owner of a domain to specify a list of servers that are allowed to send email messages with return addresses in this domain.

Mail transfer agents receiving email messages can request SPF information using a simple DNS query, thus verifying the sender's server.

The standard record looks like this: example.org. IN TXT v=spf1 +a +mx include:_spf.mx1.mirohost.net ~all

v = specifies the version of SPF used.

Then comes the list of verification mechanisms: in this case, "a" allows receiving messages from a node whose IP address matches the IP address in the A record for example.org; "Mx" allows receiving messages if the sending node is specified in one of the MX records for example.org.

The line ends with "-all" - indicating that messages that have not been verified using the listed mechanisms should be rejected.