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Sender ID (SIDF)



The Sender ID Framework is a protocol created by Microsoft to counter email domain spoofing and to provide greater protection against phishing schemes by verifying an email message's sender.

Published Standards: RFC 4406 and RFC 4407

Today, a huge majority of unwanted e-mail contains headers that lie about the origin of where that email came from. This is true of most spam and substantially all of the virus e-mail that is sent. Sender ID allows the verification of either or both the "5321.from" or the "5322.from". Whereas SPF verifies just the 5322.from.  Thus Sender ID was introduced to provide greater protection, because the 5322.from is what's displayed to users in the email client, which allows phishing and domain spoofing schemes to be effective.

How does Sender ID work?

  • You send an email message.
  • The recipient email server receives your message.
  • The recipient email server checks the SPF Record of the sending domain and determines that it's a match.
  • If the IP address and SPF record of the sending server matches the mail is delivered.

Diagram of How Sender ID Works

How Email Works Diagram

How do I set up my Sender ID record?


Sender ID uses the SPF Record or a SPF2.0 Record. If you have an SPF Record and your email software Purported Responsible Address (PRA) is derives from RFC 5322 and the MAIL FROM (Reverse-Path) derives from RFC 5321, then you don't need an SPF2.0 record. If your email software only implements one of the RFCs then you'll need to specify which one by adding a TXT record to you DNS.

If your mail server implements:

RFC 5322 ONLY: TXT/SPF = spf2.0/pra a mx a:mail.unlocktheinbox.com ip4:168.144.32.45 ?all
RFC 5321 ONLY: TXT/SPF = spf2.0/mfrom ?all
BOTH: Your normal SPF Record which you can generate here: SPF Wizard

The word "BOTH" above means, that the Sender ID will use the "v=spf1" as defined in SPF to perform the check and you don't need specific "spf2.0" (PRA) tags. However, if you wanted to add the (PRA) Sender ID records, you can, but it's unnecassary.

You can use our Sender ID Wizard to generate your SPF2.0 Records here: Sender ID Wizard

Add those records to both the TXT (TYPE 16) and the SPF (TYPE 99) in DNS (if your able), to learn more about SPF (TYPE 99) - Click Here: SPF Type 99

Once those records are added to your DNS, you can send an email to "mailtest@unlocktheinbox.com" and it will return the results, letting you know the status of SPF, DKIM, Sender ID, and Spam Assassin checks.

Source: Unlock The Inbox

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