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Writer's pictureJoe Tierney

From Trash to Inbox: How SPF, DKIM & DMARC Boost Email Deliverability


How to fix Delivery Status Notification (Failure) Message blocked


In today's digital landscape, email remains the critical communication channel for businesses. However, it's also a prime target for cybercriminals who exploit email spoofing for phishing attacks and fraudulent activities. This can damage your brand reputation, erode customer trust, and lead to financial losses.





Fortunately, a trio of email authentication protocols – SPF, DKIM, and DMARC – can bolster email security posture and keep your inbox safe from malicious actors. Let's touch on each protocol and understand how they work together.


  • SPF (Sender Policy Framework):  Think of SPF as your guest list for email senders. It establishes a whitelist of authorized email servers (like Google Workspace or Microsoft 365) permitted to send emails on your domain's behalf. This helps prevent email spoofing, where attackers disguise their email address to appear legitimate.


Here are some common SPF record examples:

* **Standard SPF Record for Google Workspace:**
    ```
    v=spf1 include:_spf.google.com ~all
    ```
    This record allows emails sent through Google Workspace servers and sets a soft fail for anything else (meaning the email might still be delivered but flagged as suspicious).
* **Standard SPF Record for Microsoft 365:**
    ```
    v=spf1 include:spf.protection.outlook.com -all
    ```
    This record allows emails sent through Microsoft 365 servers and rejects anything else (indicated by the `-all` at the end).
  • DKIM (DomainKeys Identified Mail):  Imagine DKIM as a digital signature for your emails. It employs cryptographic keys to verify the authenticity and integrity of incoming emails. Think of it as a tamper-proof seal – any alteration to the email content would invalidate the signature, exposing potential forgery attempts.




  • DMARC (Domain-based Message Authentication, Reporting & Conformance):  DMARC acts as the conductor, overseeing and orchestrating the entire email authentication process. It leverages information from SPF and DKIM to instruct email receivers on how to handle emails that fail authentication checks (e.g., quarantine or reject). Additionally, DMARC provides valuable reporting mechanisms, allowing you to receive insights into authentication failures and identify potential spoofing attempts targeting your domain.


Postmark offers a free DMARC service that will help you create the required DNS records to be configured.

Here's an example DMARC record for the DNS entry of the domain contoso.com:

v=DMARC1; p=none; rua=mailto:dmarc-reports@contoso.com;

Explanation of the record:


  • v=DMARC1: This specifies the DMARC protocol version (v=DMARC1 indicates version 1).


  • p=none: This defines the policy for handling emails that fail DMARC checks. In this example, p=none sets the policy to "none" which means reports are generated but no action is taken on failing emails (quarantine or reject). This is a good starting point for monitoring purposes before implementing stricter policies.


  • rua=mailto:dmarc-reports@contoso.com: This defines the reporting address (rua) where DMARC aggregate reports will be sent. These reports provide valuable insights into authentication failures and potential spoofing attempts targeting your domain. It's recommended to create a dedicated mailbox for these reports (e.g., dmarc-reports@contoso.com).


Benefits Beyond Security: Enhanced Deliverability and Reputation


Implementing SPF, DKIM, and DMARC isn't just about safeguarding your inbox – it also significantly improves your email deliverability. Major email providers like Google and Yahoo have implemented stricter email authentication policies, often filtering emails lacking SPF, DKIM, or DMARC verification into spam folders. By adopting these protocols, you demonstrate your commitment to email security, enhancing your sender reputation and ensuring your legitimate emails reach recipient inboxes.


Remember, meticulous planning and execution are crucial for a successful implementation. Consider consulting a qualified IT professional to ensure a smooth integration of these protocols into your email infrastructure.





Take control of your email security today! Implement SPF, DKIM, and DMARC to build a robust defense against email spoofing and phishing attempts. Protect your brand reputation, safeguard sensitive information, and ensure your emails reach the intended recipients.

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