Caller ID is a technology developed by Microsoft to reduce the amount of spam sent by email . The specification was published on February 24, 2004.
The essence of this technology is that the domain administrator specifies the IP addresses of the SMTP mail servers from which mail for this domain can be sent in the DNS system . Upon receipt of an incoming message, the mail server checks whether sending messages from the domain specified in the message is allowed from the IP address used. If the IP address of the sender is not in the list of allowed, then this means that the sender address is forged.
This technology differs from SPF in the format of records in DNS and in what address is checked.
Caller ID technology alone does not exclude the possibility of spamming , but it can improve the efficiency of gray lists to block spam .
The information needed for this technology is stored in the DNS as TXT records. The content of the field is compiled in XML format.