Enable SPF
Enables SPF detection.
Reject failures
If an incoming connection returns a SPF fail, then the email message will not be accepted by the SMTP service.
Add Received-SPF header for unauthenticated senders
Adds the Received-SPF header to all unauthenticated emails arriving via SMTP.
Pass local IP addresses (no checking will be done)
If an IP address is determined to be local, then an SPF check is not done.
Enable local white list policy
Use your own SPF white list policy. The local policy is checked when the all mechanism exists for the domain being checked and is not indicating a pass. The local policy only has an effect if it is passing the domain, so you would create an SPF that indicates requirements for domains you wish to pass. The whitelist policy can be a complete SPF record, but must exclude the SPF version string (i.e. Must not have 'v=spf1').
Apply best guess policy for domains without SPF
For connections that do not have an SPF record further checks can be added in their place. A subsequent check could be done on an MX record or even an A record for the domain lookup.
With MailEnable, the results of a SPF test are added as a header item to the email. The header is Received-SPF. SPF tests return one of seven results, which are outlined below. The added header includes the result and a brief description. If there are filters running to check the header, the first string after the header is the result. E.g. Received-SPF: none, Received-SPF: fail.
Result - Description
Pass - The email comes from a valid source.
Softfail - The email may not be from a valid source.
Fail - The email does not come from a valid source.
Neutral - The data is inconclusive in determining whether the email is coming from a valid source.
None - The domain has no SPF record.
Error - There is an error processing the SPF.
Unknown - There is an error processing the SPF.