When it comes to managing email delivery on your Sophos XG firewall, encountering bounced emails can be frustrating and disruptive. Bounced emails occur when the recipient's mail server rejects the message and returns it to the sender. This can happen due to various reasons, such as incorrect configurations, spam filters, or network issues.

In this comprehensive guide, we will explore common causes of bounced emails on Sophos XG and provide expert tips and strategies to resolve these issues effectively.

Understanding Bounced Emails

Before we dive into troubleshooting, let's first understand the different types of bounced emails:

1. Soft Bounces

Soft bounces are temporary delivery failures that can occur due to reasons like a full mailbox, a temporary issue with the recipient's mail server, or the message being too large. In most cases, soft bounces resolve themselves, and the email will be retried for delivery automatically.

2. Hard Bounces

Hard bounces are permanent delivery failures caused by issues such as an invalid or non-existent email address, a blocked domain, or a recipient's mail server rejecting the message. These issues require specific actions to resolve.

Troubleshooting Steps

Follow these troubleshooting steps to resolve bounced email issues on your Sophos XG firewall:

1. Check Email Configuration

Ensure that your email configuration settings on the Sophos XG firewall are accurate and up to date. Verify the mail server details, including the hostname, port number, and authentication settings. Incorrect configurations can lead to bounced emails.

2. Review Spam Filtering

Check your spam filtering settings on the Sophos XG firewall. Aggressive spam filtering can sometimes flag legitimate emails as spam, leading to their rejection or bouncing. Adjust the spam filter settings to ensure proper email delivery.

3. Confirm DNS Settings

Ensure that your DNS settings are correctly configured on the Sophos XG firewall. The DNS resolution is crucial for successful email delivery. Verify the DNS server addresses and test the connectivity to ensure smooth DNS resolution.

4. Monitor Blacklists

Regularly monitor blacklists to check if your domain or IP address has been listed. Being listed on a blacklist can result in your emails being bounced or marked as spam. If you find your domain or IP address on a blacklist, follow the necessary steps to delist it.

5. Analyze Delivery Logs

Review the delivery logs on the Sophos XG firewall to gather insights into the bounced emails. Look for any specific error codes or messages that can help identify the underlying issues. These logs can provide valuable information for troubleshooting.

1. Test Email Delivery

Perform test email deliveries to different recipients and monitor the results. If specific recipients consistently bounce, investigate further to identify any recipient-specific issues. This could include incorrect email addresses, strict email filters, or other configuration problems on the recipient's end.

Preventing Bounced Emails

While troubleshooting and resolving bounced emails is essential, prevention is always better than cure. Here are some preventive measures to minimize the occurrence of bounced emails:

1. Maintain a Clean Email List

Regularly clean and update your email list to remove invalid or non-existent email addresses. Sending emails to invalid addresses will result in hard bounces. Implement processes to verify email addresses during sign-ups and periodically validate your existing subscriber list.

2. Use Double Opt-In

Implement a double opt-in process for email subscriptions. This ensures that subscribers confirm their email addresses, reducing the chances of typos or incorrect addresses. Double opt-in also helps you build a more engaged and responsive email list.

3. Authenticate Your Emails

Implement email authentication protocols like SPF (Sender Policy Framework), DKIM (DomainKeys Identified Mail), and DMARC (Domain-based Message Authentication, Reporting, and Conformance). These protocols verify the authenticity of your emails and help prevent spoofing, improving email deliverability.

4. Monitor Delivery Metrics

Regularly monitor email delivery metrics like open rates, click-through rates, and bounce rates. High bounce rates can indicate potential issues with your email list or email configuration. Analyze the bounce reasons to identify patterns and take necessary actions to improve deliverability.


Bounced emails on Sophos XG can disrupt your email communication and impact your business. By following the troubleshooting steps outlined in this comprehensive guide and implementing preventive measures, you can ensure successful email delivery and minimize bounced emails. Stay vigilant, monitor your email performance, and take proactive steps to maintain a healthy and responsive email system.