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Mail Tester
SPF Records and Alignment


SPF or Sender Policy Framework is a mechanism that email service providers use to determine if a particular email server can send mail on your behalf. Make no mistake about it, anyone one can pretend to send mail from anymore, whether you own that particular email address or not. It's very simple to do and doesn't require any special tools or skills. SPF is a way to control this type of foregry and it's very easy to configure.

In order for this check to happen Mail Tester will take the last "received" header along with the 5321.FROM aka "return-path" header. It will look up the domain's SPF record under the "return path" header and validate the last "received" header (IP/Domain) and make sure they are allow to send mail on your behalf.

Since different mail servers evaluate SPF records differently, you might pass at one email service provider and fail at another. Mail Tester uses 3 different independant SPF Checkers to validate your SPF Record. If anyone of them fails it's marked as a critical error. If you don't have an SPF record it's marked as a critical error. If you SPF length is over 255 characters it will be marked as a critical error. If you have an SPF Type 99 Record which is obsolete and it doesn't match your type 16 SPF record, it will be flagged as a critical error.

Resources: SPF Record
Tools: SPF Wizard

Sender ID is consider SPF2.0 it's an expiremental standard that I believe will eventually be retired, but it was developed to allow you to also address the issue of validating the 5322.FROM in addition to the 5321.FROM.

Resources: Sender ID Record
Tools: Sender ID Wizard

SPF Email Identifier Alignment compares the domain in your 5322.FROM and your 5321.FROM, if they match exactly they are in strict alignment. If they match on the root domain only, they are in relaxed alignment. If they don't match, they are unaligned. This becomes important when setting up your DMARC Record.
 
Read out next blog in the Mail Tester Series: Mail Tester - DKIM Signatures and Alignments

The Mail Tester Pro Report - SPF Section

Publication: RFC 4408
SPF Records
ARSoft Check: Passed
SmarterMail Check: Passed
SpamAssassin Check: Passed
SPF DNS Location: Click Here: unlocktheinbox.com
SPF Record in TXT (TYPE 16): v=spf1 a mx -all
(TYPE 16) Syntax: Passed
(TYPE 16) Length: 82 Bytes
SPF Record in SPF (TYPE 99): v=spf1 a mx -all
(TYPE 99) Syntax: Passed
SPF/TXT Match: Passed
SPF Lookups: Passed

Information : Identifier Alignments
SPF Alignment Test (Used in DMARC ASPF Test)
Mail From/Return Path Domain: unlocktheinbox.com
From Domain: unlocktheinbox.com
SPF Identifier Alignment: Strict

Publication: RFC 4406
Sender ID
Sender ID Check: Passed
Sender ID Record: Uses SPF implementation above
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