Sender Policy Framework (SPF) is a validation system that allows ISPs and mail servers to check if the incoming mail has been sent from an authorized server. By using the IP address of the sending server and the DNS records of your domain, ISPs can check if the sending server is authorized. If email is coming from an unauthorized sender, the emails will be marked as spam or moved to junk.
Connection over the Internet use DNS (Domain Name System) to resolve Domain Name to the IP (Ipv4) Address . Each domain should contain MX (Mail Exchanger) in domain’s DNS Zone Record file.Th purposes of MX Record is to inform the sender email server where is the target mail server location.
SPF Job is to publish the reverse MX DNS records of the mail server , in other words SPF is like broadcasting information about the source mail server that send the mail from the domain,then the recipient mail server can check theses “published record by SPF” to insure that the incoming e-mail is coming from trusted sender or trusted domain.
SPF operates at the level of the SMTP transaction, and requires these information:
lets try to explain the simple SPF record for domain exampledomain.com
The parts of the SPF record mean the following:
v=spf1 | SPF version 1 |
---|---|
mx | the incoming mail servers (MXes) of the domain are authorized to also send mail for exampledomain.com |
a:ex1.exampledomain.com | the machine ex1.exampledomain.com is authorized, too |
-all | all other machines are not authorized ,”-” Mechanism meaning Fail |
The bellow are an overview of SPF mechanism syntax may include in the SPF record:
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