SPF

Sender Policy Framework, SPF for short, can be used to verify the sender of an e-mail. Internet Server Providers can use the SPF record to check the authorization of mail servers to send mail for a specific domain. To use SPF, an SPF record must be created in the DNS. An SPF record contains a list of IP addresses that are allowed to send emails on behalf of the domain. The SPF mechanism identifies the SPF record by using the return address of the domain. This results in the following SPF cycle:

• A sender sends an email to the receiving email server
• The server checks if the sender is on the domain's list of allowed senders
• Is this the case? Then a link is established between email domain and email
• Is this not the case? Email processing at the server will continue as usual, as anything could be going on

Why is the SPF record link missing?

There are several reasons why the sender is not listed. For example, the e-mail may be genuine, but the list of senders is incorrect or incomplete. In addition, the real e-mail may have been forwarded. This means that the e-mail may have come from a variety of IP addresses, making the list of senders of little help. Finally, the e-mail may be unwanted and fake. Because there are so many reasons that an SPF record is not complete, it becomes difficult for the server to interpret the SPF link. To fill this link, you can use DKIM. DKIM fills the technical framework and provides an additional way to link the e-mail back to a domain.