What is a 553 relay error from Symantec?

A 553 relay error from Symantec typically means their mail server has detected an unauthorized attempt to use it as an intermediary for sending email. This is often due to a misconfiguration in your mail server's MX records or routing, where it's trying to send mail through Symantec's infrastructure rather than directly to the recipient's mail server.

How does DMARC relate to Symantec email blocks?

DMARC (Domain-based Message Authentication, Reporting, and Conformance) plays a critical role in Symantec email blocks. If your DMARC record indicates that emails from your domain should be authenticated but fail SPF or DKIM checks, Symantec is likely to block or quarantine those emails to protect their users from spoofing and phishing, often citing DMARC failure as the reason.

How long does it take to get off a Symantec blacklist?

The time it takes to get off a Symantec blacklist or blocklist depends on the severity of the offense and how quickly you address the underlying issues. Minor issues might clear up in a few days to a week after corrective actions are taken, while more severe blocklistings could take weeks or even months. Consistent good sending practices are crucial for reputation recovery.

Can Symantec block emails with attachments?

Yes, Symantec can block emails with attachments. Their filters analyze attachments for malware, viruses, and suspicious file types. Even seemingly innocuous attachments can be blocked if they are password-protected, encrypted, or if the file type is commonly used for malicious purposes, such as executable files.

What is the role of MX records in Symantec blocks?

MX (Mail Exchanger) records specify the mail servers responsible for receiving email for a domain. In the context of Symantec blocks, incorrect MX record configuration can lead to relay errors, where your mail server tries to send mail through Symantec's system without permission. Proper MX record setup ensures emails are routed correctly to their final destination.

What causes a Symantec email block and how to fix it? - Troubleshooting - Email deliverability - Knowledge base

Email deliverability is a complex landscape, and encountering blocks from major security providers like Symantec (now Broadcom) is a common challenge for senders. These blocks can severely impact your communication, leading to missed opportunities and frustrated recipients. Understanding the root causes of such blocks is the first crucial step towards effective resolution.

Symantec's email security solutions, including Email Security.cloud (formerly MessageLabs), are designed to protect users from a wide range of threats, including spam, malware, and phishing attempts. While their goal is to ensure inbox safety, legitimate emails can sometimes get caught in their sophisticated filtering mechanisms, resulting in delivery failures.

Navigating a Symantec email block requires a systematic approach, from diagnosing the specific issue to implementing the necessary technical and content-based fixes. This guide will help you understand why your emails might be blocked by Symantec and provide actionable steps to restore your email flow.

Common causes of Symantec email blocks

Symantec's filtering systems are robust and consider multiple factors when evaluating incoming mail. A common reason for a block is often related to the sender's IP address or domain reputation. If your IP has a history of sending spam or exhibits suspicious sending patterns, Symantec's anti-spam rules may flag your emails as a threat and prevent their delivery.

Another significant factor is email authentication. Symantec (and Broadcom) heavily relies on SPF, DKIM, and DMARC to verify sender legitimacy. If your emails fail DMARC authentication, they are highly likely to be blocked or sent to junk folders, as this signals potential spoofing or unauthorized sending.

Content is also a key determinant. Emails containing suspicious attachments, links to malicious sites, or typical spam keywords can trigger Symantec's content filtering policies. Even legitimate emails can be blocked if their content or formatting resembles known spam characteristics.

Common content filter triggers

Suspicious attachments: Files like executables (.exe), password-protected zip files, or unusual document types.
Malicious links: URLs leading to known phishing sites, malware, or unverified domains.
Spam keywords: Phrases commonly associated with unsolicited commercial email, like "work from home" or "free money".
Poor sender reputation: A history of high bounce rates, spam complaints, or sending to invalid addresses.

Diagnosing a Symantec block

The first indication of a Symantec block often comes through bounce messages. These messages typically contain error codes and descriptions that point to the reason for non-delivery. For instance, you might see a 553 relay error, indicating that Symantec's mail server believes you are trying to use it as an unauthorized relay.

A bounce message like the one seen in community forums can look something like: "553 you are trying to use me [server] as a relay, but I have not been configured to let you do this. (#5.7.1)". This specific error suggests that your mail server might be misconfigured, attempting to send email through Symantec's servers without proper authorization, rather than delivering mail to a recipient behind Symantec.

Verifying your domain's MX records is crucial in such cases. MX records dictate which mail servers are responsible for accepting incoming mail for your domain. If your MX records are not correctly set up, or if they're trying to send directly to an intermediate Symantec server instead of the final destination (like an Office 365 mail server), you can trigger these relay errors. I recommend performing a simple MX lookup to ensure proper configuration.

Example MX record lookupbash

dig MX yourdomain.com +short

Steps to resolve Symantec blocks

Resolving a Symantec block often involves addressing the underlying cause identified during diagnosis. If it's an IP reputation issue (a common form of blacklist), you'll need to improve your sending practices. This includes cleaning your email lists to remove inactive or invalid addresses, monitoring bounce rates, and avoiding sending unsolicited mail. You might also need to submit an unblock request directly to Symantec or Broadcom's support team.

For DMARC, SPF, and DKIM related issues, ensure your DNS records are correctly configured and aligned. A properly implemented DMARC policy, especially at quarantine or reject, tells receiving servers exactly how to handle emails that fail authentication. This helps build trust with services like Symantec. You can find more information in our guide on a simple guide to DMARC, SPF, and DKIM.

If the problem is content-based, review your email templates and sending practices. Avoid excessive use of capitalization, exclamation marks, and spammy phrases. Ensure all links are reputable and attachments are necessary and safe. Sometimes, even the email's HTML structure can trigger filters, so simple, clean designs are often best.

Common causes

Poor IP reputation: Your IP address is listed on a blocklist or has a history of spam complaints.
Authentication failures: SPF, DKIM, or DMARC records are missing or incorrectly configured, leading to authentication failures.
Content issues: Email content, attachments, or links trigger Symantec's spam filters.
MX record misconfiguration: Attempting to relay through Symantec's servers when not configured to do so.

Solutions

IP warming & list hygiene: Gradually increase sending volume and maintain a clean email list. Monitor for blocklist status.
Implement DMARC, SPF, DKIM: Ensure all authentication records are valid and in alignment.
Optimize content: Review and refine email copy, links, and attachments to avoid spam triggers. Use clear, concise messaging.
Correct MX records: Ensure your domain's MX records point correctly to your legitimate mail servers.

Maintaining long-term email deliverability with Symantec

Achieving and maintaining good email deliverability with Symantec requires ongoing effort. Regularly monitor your IP and domain reputation. Tools for blocklist monitoring can alert you to issues before they escalate, helping you detect if your IP address is blacklisted (or blocklisted).

Focus on list hygiene by periodically removing unengaged subscribers and invalid email addresses. Sending to a clean, engaged list reduces bounce rates and spam complaints, which are key indicators for Symantec's filters. Implementing double opt-in for new subscribers is also a strong best practice.

Proactive DMARC monitoring is essential. Analyzing your DMARC reports from services like Google and Yahoo provides insights into authentication failures and potential spoofing attempts, allowing you to quickly identify and fix issues that could lead to Symantec blocks. For further reading, check out our guide on how to improve email delivery rates to corporates.

Aspect	Description	Benefit
Authentication	Ensure SPF, DKIM, and DMARC are correctly set up and aligned.	Boosts sender credibility, reducing the likelihood of blocks.
List hygiene	Regularly clean email lists, remove inactive subscribers, and use double opt-in.	Minimizes bounces and spam complaints, improving sender reputation.
Content quality	Create engaging, relevant, and well-formatted emails without spam triggers.	Enhances user experience and reduces likelihood of content-based filtering.
Monitoring	Continuously track DMARC reports and check for blocklist (blacklist) listings.	Enables early detection and quick resolution of deliverability issues.

Views from the trenches

Best practices

Regularly review your email sending infrastructure configuration, especially MX records, to ensure they are pointing to the correct mail servers and not attempting unauthorized relays.

Implement and maintain robust email authentication (SPF, DKIM, DMARC) to prove the legitimacy of your emails and reduce the chances of being flagged by Symantec's filters.

Segment your email lists and send targeted content to engaged subscribers to minimize spam complaints and maintain a positive sender reputation.

Actively monitor your IP and domain status on major email blacklists and blocklists, allowing for quick response to any new listings.

Keep your email content clean, relevant, and free from characteristics commonly associated with spam to pass content filters.

Common pitfalls

Ignoring bounce messages, which often contain crucial details about why Symantec or other providers are blocking your emails, can lead to prolonged deliverability issues.

Assuming that MX priority values will be strictly honored by all receiving mail servers; many ignore them, leading to unexpected routing.

Failing to update DMARC, SPF, and DKIM records after migrating email services or changing sending platforms, causing authentication failures.

Sending to outdated or unverified email lists, which increases hard bounces and spam trap hits, negatively impacting your sender reputation.

Using generic email content or subject lines that resemble known spam patterns, triggering automated content filters.

Expert tips

Always consult the exact bounce message for specific error codes, as they provide the most accurate indication of why Symantec blocked the email.

When troubleshooting, check if the remote machine is trying to relay the email through Symantec or simply deliver to a recipient behind their service.

Even if your MX records show priorities, some mail servers may not honor them, so prepare for varied routing behaviors.

Misconfigurations like public-facing Microsoft 365 MX records when behind a service like MessageLabs can lead to unexpected relay issues.

Spamtrap domains sometimes appear in MX records with very high preference numbers, designed to catch malicious senders who try all listed MXes.

Expert view

Expert from Email Geeks says if you are not trying to send email through Symantec's servers as a relay, then the issue is likely a local site misconfiguration.

2021-02-12 - Email Geeks

Expert view

Expert from Email Geeks says that MX weight or priority means nothing at all in the real world, as it is a nice idea honored by some mail servers and ignored by most.

2021-02-12 - Email Geeks

Strengthening your email deliverability

Dealing with Symantec email blocks can be frustrating, but with a clear understanding of the common causes and a systematic approach to troubleshooting, these issues are resolvable. Whether it's an IP reputation problem, an authentication failure, or a content-related trigger, identifying the exact bounce message is key.

Prioritizing strong email authentication, maintaining clean sending lists, and ensuring your email content is compliant are fundamental practices for avoiding Symantec (and other provider) blocks. Remember that consistent monitoring and proactive adjustments to your email program are essential for long-term deliverability success.

By implementing these strategies, you can not only resolve current blocks but also strengthen your overall email deliverability, ensuring your messages reliably reach their intended inboxes.