Sender Policy Framework (SPF) is an open standard to prevent
sender address forgery. SPF protects the envelope address of a sender,
which is used for the delivery of email messages. Trend Micro Email
Security allows you to verify the sender's
authenticity using SPF settings.
SPF requires the owner of a domain to publish the email sending
policy (for example, which email servers are used to send email messages from that
domain) in an SPF record in the Domain Name System (DNS).
When Trend Micro Email
Security receives an email
message claiming to come from that domain, Trend Micro Email
Security checks the SPF record to verify whether the email message complies with the
domain's stated policy. For example, if the message comes from an unknown server,
the email message can be considered as fake.
Evaluation of an SPF record can return any of the following
results.
|
Result
|
Explanation
|
Default Action
|
|
Pass
|
The SPF record designates the host to be
allowed to send.
|
Accept (reserved)
|
|
Fail
|
The SPF record has designated the host as not
being allowed to send.
|
Delete (customizable)
|
|
SoftFail
|
The SPF record has designated the host as not
being allowed to send but is in transition.
|
Accept (customizable)
|
|
Neutral
|
The SPF record specifies explicitly that
nothing can be said about validity.
|
Accept (customizable)
|
|
None
|
The domain does not have an SPF record or the
SPF record does not evaluate to a result.
|
Accept (customizable)
|
|
PermError
|
A permanent error has occurred (for example,
badly formatted SPF record).
|
Accept (customizable)
|
|
TempError
|
A transient error has occurred.
|
Accept (customizable)
|
 |
NoteBy default, if an email message gets a "Pass" result, Trend Micro Email
Security will bypass the SPF check and skip the
remaining SPF settings for the message. Trend Micro Email
Security will then continue scanning the message according to policy rules.
If an email message passes the Sender IP Match check, the message is
also considered as passing its own SPF check.
|