Sender Policy Framework (SPF)
SPF is the abbreviation for Sender Policy Framework. It is
a technique for email authentication that uses DNS. It aids in ensuring that
spammers are not able to send messages on one’s domain’s behalf. Authorized
mail servers can be published by an organization with SPF. When SPF is combined
with the information that is related to DMARC (Domain-based Message Authentication,
Reporting & Conformance), a receiver or the receiving systems have the
information regarding the trustworthiness of an email’s origin. This enables an
email sender to specify the email servers that are permitted to send email on
behalf of the email sender’s domain. When an SPF record is there, Internet
Service Providers are able to ascertain that a specific mail server is
authorized for the purpose of sending email for a particular domain. An SPF
record is a DNS TXT record. It contains a list of those IP addresses that are
permitted to send email on one’s domain’s behalf.
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How SPF works?
In order to reap the benefit of SPF, an SPF record is published in the DNS. This is a record that has a list of all the IP addresses that can send email on the domain’s behalf. In order to identify the SPF record, the domain that is in the return-path address is used by the SPF mechanism. At the time when a sender attempts to transfer an email to an email receiving server for the purpose of its delivery, the server ascertains if the particular sender is present in the domain’s list that is about such senders that are allowed to do so. If it is, then a link gets established between the email and the email domain. If it isn’t, then the server processes this email as usual, sans this link.
SPF requires three information. These are mentioned below.
The MAIL FROM: parameter
of an incoming mail
The HELO or EHLO
parameter of the sending SMTP server
The IP address of the sending SMTP server
Limitations of SPF
SPF has certain limitations which are mentioned in this
section. The “From” header is not validated by SPF. This header appears in most
clients as the message’s sender. SPF uses the “envelope from” for the purpose
of determining the sending domain. In the event that an email is forwarded, SPF
will break. This results in the “forwarder” becoming the new “sender” of that
particular message and eventually leads to a failure of the SPF check that is
performed by the new destination. Last but not the least, reporting isn’t
present in SPF. This makes it difficult to maintain.
Benefits of SPF
SPF has become crucial with regard to verifying the sending
infrastructure that can relay email on behalf of one’s domain. The main
benefits that can be reaped by implementing SPF for email are that it combats
email spoofing and domain impersonation, increases one’s emails’ overall
deliverability as well as boosts the reputation of one’s brand.
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