SMTP Protocol Basics for IT and Cybersecurity Professionals

SMTP Protocol Basics for IT and Cybersecurity Professionals

The Simple Mail Transfer Protocol (SMTP) is the foundational communication protocol for sending electronic mail across the Internet. Developed by the Internet Network Working Group and standardized in multiple key RFCs—most notably RFC 5321—SMTP governs the process of email transmission between email clients, mail servers, and intermediary systems. As digital communication has become ubiquitous, SMTP’s importance in ensuring the reliable delivery of electronic messages cannot be overstated.

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Is p=reject the ultimate DMARC policy? 5 situations in which you should implement it

Is p=reject the ultimate DMARC policy? 5 situations in which you should implement it

Is p=reject the ultimate DMARC policy? 5 situations in which you should implement it

by DuoCircle

 

Out of the three DMARC policies—“p=none”, “p=quarantine”, and “p=reject” each serves a different purpose and provides a different level of security. But when it comes to actively blocking emails that attempt to spoof your domain, the strictest policy, “p=reject,” is the best choice.

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Microsoft 2025 Fixes, Chrome Zero-Day, Enterprise Security Flaws – Cybersecurity News [December 08, 2025]

Microsoft 2025 Fixes, Chrome Zero-Day, Enterprise Security Flaws – Cybersecurity News [December 08, 2025]

Microsoft 2025 Fixes, Chrome Zero-Day, Enterprise Security Flaws – Cybersecurity News [December 08, 2025]

by DuoCircle

 

Cyber incidents this week spanned operating systems, browsers, enterprise platforms, hardware, and developer tooling. Microsoft closed out the year patching 56 Windows flaws and three zero days, while Google rushed an emergency fix for an actively exploited Chrome bug. Fortinet, Ivanti, and SAP shipped critical updates for auth bypass and RCE risks, and new PCIe IDE weaknesses prompted firmware work from Intel and AMD. At the same time, a Gogs zero day and abused GitHub tokens highlighted ongoing threats to software supply chains.

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DKIM Authentication Explained: Securing Your Email With Verified Signatures

DKIM Authentication Explained: Securing Your Email With Verified Signatures

DomainKeys Identified Mail (DKIM) is a well-established email authentication protocol designed to help organizations defend against email spoofing, phishing attacks, and business email compromise (BEC). When implemented correctly, DKIM authentication allows the recipient’s email server to verify that a signed email has genuinely originated from the stated domain and that its message content has not been tampered with during transit.

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SPF Syntax Made Simple: Creating Accurate and Effective SPF Records

SPF Syntax Made Simple: Creating Accurate and Effective SPF Records

 

Sender Policy Framework (SPF) is a core email authentication protocol designed to enhance email security. SPF records play a crucial role in protecting domains from phishing, spoofing, and impersonation attacks by specifying which mail servers are authorized to send on behalf of a domain. When properly configured, SPF authentication significantly improves deliverability, helping emails avoid spam folders used by providers such as Gmail and Yahoo.

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SPF records updated by Google: Here’s what domain owners need to know!

SPF records updated by Google: Here’s what domain owners need to know!

SPF records updated by Google: Here’s what domain owners need to know!

by DuoCircle

 

Does your SPF record include Google as an authorized sender? If yes, then you must be dependent on Google’s recommended ‘include:_spf.google.com’ entry to make the most out of the SPF protocol. Recently, this entry has been updated by Google. So, if your domain has outdated or custom configurations, then the latest update may cause certain issues. This blog aims to explore the update in detail and the tactics that can be used to avoid any potential email deliverability hassles.

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What is MTA-STS (Mail Transfer Agent Strict Transport Security) and why do you need it?

What is MTA-STS (Mail Transfer Agent Strict Transport Security) and why do you need it?

What is MTA-STS (Mail Transfer Agent Strict Transport Security) and why do you need it?

by DuoCircle

 

We have heard so much about securing your outgoing emails, but the truth is, attackers can even enter your digital ecosystem through emails that are sent to your organization. This means your incoming emails are just as unsafe as your outbound ones. 

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