What steps can I take to stop someone from spoofing my email address?
Michael Ko
Co-founder & CEO, Suped
Published 25 Jun 2025
Updated 16 Aug 2025
7 min read
Email spoofing is a pervasive problem that can significantly damage a brand's reputation and lead to serious security risks. It occurs when malicious actors send emails that appear to originate from a legitimate source, often by forging the sender's address. While it's impossible to completely prevent someone from simply typing your email address into the From field of an email client, there are robust measures you can take to ensure that such spoofed emails are rejected by receiving mail servers.
My focus here is on the technical and operational steps you can implement to protect your domain and prevent spoofed emails from reaching inboxes. We'll delve into authentication protocols and other strategies that fortify your email defenses.
Email spoofing takes advantage of the original Simple Mail Transfer Protocol (SMTP) design, which lacked built-in authentication mechanisms. This fundamental flaw allows senders to fabricate the From address, making an email appear as if it came from a legitimate source, even when it did not. This is particularly problematic for businesses, as it can be used in phishing campaigns, malware distribution, and other cyberattacks that tarnish brand trust.
It's crucial to differentiate between two common scenarios when your email address is used without your permission: when the actual From address (header from) is spoofed, and when only the Reply-To address is set to your domain. While the former is more directly addressed by email authentication protocols like DMARC, the latter requires different considerations.
Understanding these nuances helps in selecting the right defensive strategies to protect your domain from being used for malicious purposes, and to identify the source of unsolicited emails if they occur. If you receive emails appearing to be from your domain but weren't sent by you, the first step is to analyze the email headers to understand their true origin.
From address spoofing
This involves bad actors altering the From header (RFC5322.From) to display your domain, making it appear as if the email originated from your legitimate sender. This type of spoofing directly undermines your domain's credibility.
Impact on deliverability: Emails often fail DMARC authentication if your policies are properly configured, leading to rejection or quarantine by receiving mail servers.
In this scenario, the actual sender's domain is different, but they set your email address or domain in the Reply-To header (RFC5322.Reply-To). This means replies to the email will go to your legitimate address, even though you didn't send the original message.
Impact on deliverability: DMARC (and SPF/DKIM) typically do not check the Reply-To header. This means emails with a spoofed Reply-To can still be delivered, causing confusion and potential harm to recipients.
Prevention: Requires stricter internal email filtering rules, user education, and reporting to relevant authorities. DMARC will not protect your Reply-To address.
Implementing email authentication protocols
The foundation of preventing email spoofing for your domain lies in properly configuring and enforcing email authentication protocols. These DNS records help receiving mail servers verify that an email claiming to be from your domain is, in fact, authorized to send on its behalf. SPF (Sender Policy Framework), DKIM (DomainKeys Identified Mail), and DMARC (Domain-based Message Authentication, Reporting, and Conformance) are the three pillars of modern email security. Mailpro offers a guide to prevention techniques.
Your DMARC policy is the most critical component for stopping From address spoofing. When set to p=reject (or p=quarantine), it instructs receiving mail servers to take action against emails that fail SPF or DKIM authentication for your domain. This effectively blocks unauthorized senders from using your domain in the From field. For a comprehensive overview, review SolCyber's article on spoofing prevention.
A common configuration mistake is setting sp=none in your DMARC record. This means your policy (e.g., p=reject) does not apply to subdomains. If your domain is example.com and you have a DMARC record, but a spammer uses sales.example.com to spoof, the sp=none setting would allow those spoofed subdomain emails to potentially bypass your primary domain's DMARC policy. Always aim for a p=reject and ideally sp=reject for maximum protection.
Even with a p=reject policy, continuous DMARC monitoring is essential. DMARC reports provide valuable insights into email flows, showing you which IPs are sending mail on your behalf (authorized or unauthorized) and how receiving servers are handling those emails. These reports help you identify ongoing spoofing attempts and fine-tune your authentication records. It's a continuous process of observation and adjustment to maintain email security.
Beyond email authentication
While authentication protocols are foundational, stopping someone from spoofing your email address also involves a multi-layered approach that extends beyond DNS records. Think about other potential vulnerabilities that attackers could exploit to impersonate your brand.
One often overlooked vector for spoofing or unauthorized email sending is vulnerable web forms. Spammers can abuse Share with a Friend forms, contact forms, or newsletter sign-ups to inject spam content, which then gets sent using your legitimate (and authenticated) sending infrastructure. This means the emails pass SPF/DKIM/DMARC checks because they are sent from your authorized servers, even though the content is malicious. Regularly audit your website forms for potential abuse and implement CAPTCHAs, rate limiting, and other anti-bot measures.
Educating your recipients is another crucial step. Even with the strongest technical defenses, some sophisticated attacks or emails with a spoofed Reply-To might still reach an inbox. Train your employees and customers to scrutinize sender information, look for subtle discrepancies in domain names (e.g., yourd0main.com instead of yourdomain.com), and report suspicious emails. This human firewall can be incredibly effective.
Best practices for email security
Regularly monitor your domain reputation: Keep an eye on your Google Postmaster Tools dashboard and other tools to detect unusual sending patterns or issues that could indicate spoofing.
Implement strong password policies: Ensure all email accounts associated with your domain have complex, unique passwords and enable multi-factor authentication (MFA) to prevent unauthorized access that could lead to internal spoofing.
Stay informed about threats: Cybersecurity threats evolve. Staying updated on new spoofing techniques and phishing scams helps you proactively adjust your defenses. Knowledge is a key defense against these attacks.
What to do if spoofing occurs
If you discover that your email address is being spoofed, taking immediate action is important. While technical controls are in place to prevent future incidents, responding effectively to current attacks can mitigate damage to your reputation and protect your contacts.
The first critical step is to obtain the full email headers of any spoofed emails. These headers contain vital information about the email's true origin, including the sending IP address and any authentication results (SPF, DKIM, DMARC) that indicate failure. Without headers, it's challenging to trace the source or confirm if DMARC policies are being honored by the receiving mail server. You can use tools to analyze the email headers to find out more.
Once you have the header information, you can analyze it to identify the compromised IP or domain, if any, and report it. While you may not be able to stop the spoofing at the source directly, ensuring your DMARC policy is at p=reject means that most major inbox providers will block these unauthorized emails, effectively minimizing their reach and impact. You should also be proactive about checking for your domain or IP on a blacklist (or blocklist) to ensure deliverability.
For instances where web forms are being abused to send spam from your authenticated infrastructure, work with your web development team to implement robust anti-spam measures. This includes CAPTCHAs, honeypots, and server-side validation to prevent automated submissions. Regularly auditing your site for vulnerabilities is a preventative measure against such attacks, which can also include preventing fake email registrations and other forms of abuse.
Views from the trenches
Best practices
Always implement DMARC with a p=reject policy for your main domain to block unauthorized senders.
Configure sp=reject in your DMARC record to protect all subdomains from being spoofed.
Regularly monitor your DMARC reports to identify new sending sources and detect spoofing attempts.
Common pitfalls
Leaving DMARC at p=none or p=quarantine indefinitely, which allows spoofed emails to still reach inboxes.
Ignoring the sp=none tag in DMARC, leaving subdomains vulnerable to spoofing attacks.
Failing to review DMARC aggregate and forensic reports, missing critical insights into email abuse.
Expert tips
DMARC will not protect your Reply-To address from being spoofed, only the From header.
Relentless pursuit of takedowns for persistent spoofing can eventually tire out attackers.
Abuse of web forms is a growing vector for spam where authenticated emails are used by attackers.
Expert view
Expert from Email Geeks says that if your DMARC policy is at p=reject, and all legitimate mail is properly authenticated, there's not much more to do on your end. The responsibility then falls on the receiving domains to honor your DMARC policy.
2022-03-22 - Email Geeks
Expert view
Expert from Email Geeks says that DMARC will not protect against the use of your domain in the Reply-To header.
2022-03-22 - Email Geeks
Protecting your brand’s email integrity
While completely eradicating email spoofing (or email blocklist issues) is a challenging task due to the inherent nature of email protocols, you have powerful tools at your disposal to significantly limit its impact on your brand. By prioritizing strong email authentication with SPF, DKIM, and especially DMARC set to an enforcement policy (like p=reject), you send a clear signal to receiving mail servers about how to handle unauthorized emails from your domain.
Beyond technical configurations, maintaining vigilance through DMARC report monitoring, securing web applications, and educating your audience are vital. These combined efforts create a robust defense, protecting your sender reputation and helping ensure that your legitimate emails reach their intended recipients without being confused with fraudulent messages.
