Why do email services rewrite headers for legitimate emails?

Email services or marketing platforms might rewrite headers for several reasons, primarily to ensure emails pass authentication checks like SPF and DKIM. This helps prevent legitimate emails from being flagged as spam or phishing. It's often done to improve email deliverability and maintain sender reputation when using shared sending infrastructure.

Can a phishing email still seem legitimate even with header rewriting?

If a legitimate service rewrites headers, a phishing email might still appear authentic if the malicious actor exploits a vulnerability or uses a compromised account. Attackers are constantly evolving, finding ways to bypass security measures. This is why a combination of technical awareness and behavioral checks is important.

What non-technical signs can help identify phishing emails?

Beyond header inspection, look for generic greetings, spelling or grammar errors, and a sense of urgency. Hover over any links to check the true destination URL before clicking. Also, be suspicious of unexpected attachments or requests for sensitive information. Learn more about how to identify phishing emails .

How does DMARC help with phishing when headers are rewritten?

DMARC helps protect against spoofing by allowing domain owners to tell receiving email servers how to handle emails that fail authentication. While header rewriting by legitimate services can make direct inspection difficult for users, DMARC works at a server level to enforce policies. Proper DMARC configuration reduces the chances of spoofed emails reaching the inbox.

What should I do if I receive a suspected phishing email?

If you suspect a phishing email, do not click any links or open attachments. Delete the email immediately. You can also report it to your email provider or your organization's IT security team. For more general advice, see why your emails are going to spam , as some phishing detection mechanisms are similar to spam filters.

How can normal people identify phishing emails when services rewrite headers? - Compliance - Email deliverability - Knowledge base

Phishing emails are a constant threat, and they're getting increasingly sophisticated. What makes it even harder is when legitimate email services or marketing platforms rewrite email headers. This practice, often done for deliverability or compliance reasons, can obscure the true origin of an email, making it tough for an average person to tell if a message is legitimate or a malicious scam. It's a challenge many of us face daily.

The problem isn't just about technical intricacies, it's about the everyday user trying to navigate a complex digital landscape. While email authentication protocols like SPF, DKIM, and DMARC are crucial for verifying sender identity, their technical details are often hidden or abstracted by email clients. This means relying solely on inspecting email headers for phishing detection is becoming less straightforward. We need to look beyond the surface to protect ourselves.

Understanding header rewriting

Often, the first thing people check is the 'From' address. However, attackers can easily spoof this, making an email appear to come from a trusted source. Additionally, legitimate services might rewrite the From header to manage sending reputation or ensure authentication, which means what you see might not be the original sender's exact domain. This is why a closer look at other elements is essential, especially when services like

Mailchimp or

SendGrid are in play.

Even with header rewriting, email authentication mechanisms such as DMARC, SPF, and DKIM remain foundational. These protocols work behind the scenes to verify if an email sender is authorized to send on behalf of a domain. While users might not directly see the raw authentication results in their inbox, a properly configured DMARC policy can help mailbox providers filter out many spoofed messages before they reach your inbox. Sometimes, a legitimate email might still trigger a phishing warning, for reasons like problematic Gmail phishing warnings.

Even with header rewriting, certain elements in the full email header can still offer clues. Look for the Return-Path header, which indicates where bounces should be sent. Phishers might have difficulty controlling this in a way that truly masks their origin. Additionally, inspecting the Received headers can show the path the email took, though this can be very technical. Microsoft email headers in particular often reveal valuable spam classification data.

Recognizing non-technical red flags

Beyond technical headers, there are often clear non-technical signs. Look for a sense of urgency or threats, like warnings that an account will be closed if you don't act immediately. Phishers rely on triggering an emotional response to bypass your rational judgment. Always pause and consider why an email is pressuring you to act quickly.

Another common red flag is poor grammar, spelling mistakes, or awkward phrasing. While even legitimate communications can have errors, a high number of noticeable mistakes is a strong indicator of a scam. Also, be wary of generic greetings such as 'Dear Customer' instead of your specific name. Legitimate organizations typically personalize their communications when dealing with sensitive information or account actions. You can find more tips on recognizing and avoiding phishing scams from the

FTC.

Unexpected emails, even from familiar senders, should raise suspicion. If you receive an email from your bank, a known company, or even a colleague that seems out of place or requests unusual actions, it's worth a second look. Always consider the context, especially if the email contains a link or an attachment. Even with rewritten headers, these behavioral cues are often easier for a normal person to spot.

Inspecting links and attachments carefully

One of the most critical steps you can take is to carefully examine any links or attachments before clicking or downloading. Phishing emails almost always contain malicious links designed to steal your credentials or install malware. Even if the display text of a link looks legitimate, the underlying URL might be entirely different. You can protect yourself from phishing by following simple advice from

Microsoft.

To check a link, simply hover your mouse cursor over it (do not click) and observe the URL that appears in the bottom left corner of your browser or email client. If the hovered URL doesn't match the expected destination, or if it looks suspicious (e.g., unusual characters, wrong domain), it's likely a phishing attempt. Malicious links might also hide behind shortened URLs, so exercise extra caution with those.

Attachments are another common vector for phishing attacks. If an email, especially an unexpected one, asks you to open an attachment, think twice. These files can contain malware, ransomware, or other harmful software. Always verify the sender and the context before opening any attachment, even if it appears to be from someone you know. When in doubt, it's safer to err on the side of caution.

Leveraging technical indicators (when accessible)

While email services might rewrite headers, a key element for security professionals is the Authentication-Results header. This header often summarizes the SPF, DKIM, and DMARC checks performed by the receiving server. Look for results that indicate fail or softfail for these checks, especially for DMARC. A DMARC pass with p=reject or p=quarantine is a strong indicator of legitimacy, while a fail often points to spoofing. However, keep in mind that phishing emails can sometimes pass these checks if the sender's domain is compromised.

While it can be complex for a normal person, understanding the basics of how these authentication mechanisms work can empower you to ask the right questions or use available tools. For example, if you're concerned about a suspicious email, you might view its raw headers to look for the Authentication-Results or Received lines. Most email clients offer an option to show original or view source for an email.

Additionally, a domain's sender reputation is key. If a domain is on a public blocklist (or blacklist), it's a huge red flag. You can often check this using a blocklist checking service to see if the sending IP or domain has a poor reputation. A blacklisted email means it's likely involved in spam or phishing.

A layered approach to identification

Given the challenges of header rewriting, the most effective approach for an everyday user is to combine technical checks (if comfortable) with a strong emphasis on behavioral cues. Always maintain a healthy skepticism towards unexpected or overly urgent messages. If something feels off, it probably is. The goal is to make it as difficult as possible for phishers to succeed.

Empowering yourself with knowledge about phishing tactics and staying informed about common scams is your best defense. Remember, even with sophisticated attacks and header manipulations, many phishing attempts still rely on social engineering and easily detectable inconsistencies. Your vigilance is the first and most important line of defense against these evolving threats.

Views from the trenches

Best practices

Always check the full URL by hovering over links before clicking, even if the display text appears legitimate.

Verify the sender's identity through an alternative communication channel if an email seems suspicious, especially if it requests sensitive information.

Enable two-factor authentication (2FA) on all your important accounts to add an extra layer of security against compromised credentials.

Common pitfalls

Clicking on links or opening attachments from unexpected emails without first verifying the sender or the context.

Ignoring generic greetings or grammatical errors, as these are common indicators of phishing attempts.

Assuming an email is legitimate just because the 'From' address looks correct, due to header rewriting by services.

Expert tips

Prioritize email client security features, such as built-in spam and phishing filters, as they constantly adapt to new threats.

Regularly review your email settings for any forwarding rules or unauthorized access that could indicate a compromise.

Educate yourself on common social engineering tactics used by phishers, as these evolve frequently.

Marketer view

Marketer from Email Geeks says that normal users don't typically scrutinize the sending address or domain as closely as deliverability experts do. They are more likely to notice if the email content, grammar, or formatting is off.

2024-09-06 - Email Geeks

Marketer view

Marketer from Email Geeks says that when an email service rewrites headers, the sender might not even be aware it's happening, especially if their reply-to address is a generic email account like Gmail.

2024-09-07 - Email Geeks

Protecting yourself in the evolving phishing landscape

Identifying phishing emails in an environment where legitimate services rewrite headers demands a shift in approach. It's no longer just about checking the visible 'From' address or delving deep into raw headers, which can be overly technical for most people. Instead, a combination of awareness about common phishing tactics and attention to behavioral and contextual cues becomes paramount.

By focusing on suspicious links, unexpected requests, urgency, and inconsistencies in language or formatting, ordinary users can significantly improve their ability to detect fraudulent messages. While authentication protocols provide a foundational layer of security, personal vigilance remains the most powerful tool against phishing attacks. Stay informed, stay skeptical, and always verify before you click.