How to fix '550 Mismatching sender domains' error when setting up custom SMTP in Prestashop?
Michael Ko
Co-founder & CEO, Suped
Published 31 Jul 2025
Updated 16 Aug 2025
9 min read
Encountering the "550 Mismatching sender domains" error when setting up custom SMTP in Prestashop can be a frustrating experience. Unlike more common SMTP errors, this specific message often originates from Prestashop's internal validation rather than directly from the mail server. This means standard troubleshooting steps might not immediately resolve the issue. We'll explore the common reasons behind this error and provide a comprehensive guide to fix it, ensuring your Prestashop emails are sent reliably.
The error suggests that the sender domain configured in Prestashop does not align with what your SMTP server expects or allows for relaying. This can be due to various reasons, from simple typos to complex DNS configurations or server-side restrictions. Understanding the root cause is crucial for a lasting solution. We'll walk you through diagnosing and rectifying this specific domain mismatch problem.
Proper email deliverability is vital for any e-commerce store, as it directly impacts customer communication, order confirmations, and marketing efforts. An unresolved email deliverability issue can lead to lost sales and decreased customer trust. By the end of this guide, you should have a clear path to resolving the "550 Mismatching sender domains" error and achieving seamless email flow for your Prestashop store.
Understanding the '550 mismatching sender domains' error
A 550 SMTP error typically means that the recipient's mail server has rejected your message. While general 550 errors can cover a wide range of issues, the specific addition of "Mismatching sender domains" points directly to a problem with how Prestashop is presenting your sending domain to the SMTP server. The server (or Prestashop itself) is detecting a discrepancy between the domain stated as the sender and the domain it expects to be sending from.
This error is less about traditional SMTP authentication failures (like incorrect username/password) and more about the domain alignment. Your mail server might be configured to only allow sending from specific domains, or your Prestashop setup might be sending a FROM address that isn't recognized as authorized for the connected SMTP account. It's similar to getting a "550 sender verify failed" error (or blocklist), where the sending identity is questioned.
In essence, the problem is a mismatch between the domain specified in the Mail domain name field in Prestashop's email settings and the domain of the email address used for SMTP authentication. This is a common pitfall in e-commerce platforms that manage email sending directly.
Common causes for sender domain mismatch
The primary cause is often a discrepancy between the domain of the email address you're authenticating with the SMTP server and the domain set in Prestashop's Mail domain name field. For example, if your SMTP username is shop@example.com, but Prestashop is configured with a Mail domain name of yourshop.net, this conflict can trigger the 550 error.
Another common cause is an incorrectly configured FROM address in the Prestashop email template or core files. Some Prestashop versions or specific modules might override the main email configuration, leading to a sender address that doesn't match the authenticated domain. For instance, older Prestashop versions might have a hardcoded FROM field in their Swift Mailer library files.
Less common, but still possible, are issues with your DNS records, such as an invalid sender domain or reverse DNS (PTR record) not being correctly set up for your sending IP. While the error message usually points to Prestashop's internal check, a mail server could also be performing a strict check on the sender's identity and rejecting it, potentially due to the IP address being on a blocklist (or blacklist).
Step-by-step troubleshooting guide
The first step is to meticulously check your Prestashop email configuration. Navigate to Advanced Parameters > E-mail. Ensure the Mail domain name matches the domain of the email address used for your SMTP username and FROM address. This is the most frequent culprit for this specific error.
Next, verify that your SMTP server details, including the server address, port, and encryption method (SSL/TLS), are correct. Incorrect settings can also lead to communication issues, even if the domain mismatch isn't the primary cause. Double-check the email account you're using for SMTP authentication, ensuring it actually exists and has the correct credentials, as suggested in hosting documentation.
If the issue persists, examine your email templates and modules. Sometimes, a custom template or third-party module might hardcode a sender email address that conflicts with your main configuration. If you recently installed a new module or updated Prestashop, consider temporarily disabling new additions to see if the problem resolves. You should also ensure that your SPF authentication is correctly aligned with your sending domain to prevent deliverability issues.
Check email settings: Go to Advanced Parameters > E-mail in your Prestashop admin. Ensure all fields are correct, especially Mail domain name.
Verify sender email: Make sure the email address used for sending (shop email) matches the domain of your SMTP account credentials.
SMTP authentication: Confirm that your SMTP username and password are correct and that the email account is authorized to send from the specified domain.
Advanced debugging techniques
Typical problems
Mismatching Domains: The sender domain in Prestashop doesn't match the SMTP authenticated domain.
Incorrect configuration: Typo in SMTP server, port, encryption, or authentication details.
Hardcoded sender: Prestashop core files or modules overriding the sender address.
IP Blocklisting: Your sending IP is on an email blocklist (or blacklist), causing rejection.
If basic checks don't resolve the error, it's time to dig deeper. The 550 Mismatching sender domains message is specific enough to suggest Prestashop's internal logic is flagging something. You may need to inspect the core Prestashop files responsible for email sending, particularly those related to the Swift Mailer library if your version uses it.
Consider using a command-line tool like swaks (Swiss Army Knife for SMTP) to test your SMTP server directly, bypassing Prestashop. This can help isolate whether the issue lies within Prestashop or your SMTP provider. Use the --from and --to parameters to simulate the sender and recipient addresses exactly as Prestashop would send them.
If swaks works, it strongly indicates a Prestashop-specific configuration issue. In this case, examining Prestashop's debug logs or even temporarily enabling more verbose logging can provide clues. Sometimes, the problem could also be related to your domain's reputation or if your IP has landed on an email blocklist (or blacklist), which might be causing the SMTP server to reject messages with a generic 550 error, although the specific "mismatching sender domains" points away from this.
Further considerations and solutions
Prestashop settings review
Mail domain name: Ensure this is the same as your SMTP sender domain.
SMTP credentials: Verify accuracy of username, password, server, and port.
Manual file inspection
If standard settings don't fix it, delve into Prestashop's core files. Check for hardcoded FROM addresses in /tools/swift/Swift/Message.php or similar paths within the Prestashop directory. Updating these manually (with caution and backups) may be necessary for older versions or specific setups. Always clear the Prestashop cache after making any changes.
For personal emails going to spam from a custom domain, the root cause can also be domain reputation or authentication issues, not just a configuration mismatch. Ensure your domain has proper SPF, DKIM, and DMARC records set up. These records help mail servers verify that your emails are legitimate and reduce the chances of them being flagged as spam.
If your Prestashop is sending from a shared hosting environment, or if your server's IP address has been compromised, it might land on a public blocklist (or blacklist). This can lead to your emails being rejected by recipient servers, sometimes with generic 550 errors. Regularly checking blocklists for your sending IP can help identify and remediate such issues.
Views from the trenches
Best practices
Always ensure the 'Mail domain name' in Prestashop matches the authenticated SMTP sender domain.
Regularly test your email configuration after any updates or changes to Prestashop or your SMTP service.
Implement SPF, DKIM, and DMARC for your sending domain to improve email authentication and deliverability.
Common pitfalls
Ignoring error messages: The 550 message, even if vague, points to a specific issue.
Not checking Prestashop's internal settings, assuming the issue is solely with the SMTP server.
Using a generic sender email address (e.g., info@yourdomain.com) without proper authentication setup.
Expert tips
Use a dedicated transactional email service for Prestashop for better deliverability and easier troubleshooting.
Keep Prestashop and all modules updated to benefit from the latest bug fixes and security patches.
If debugging with 'swaks', ensure you're replicating the exact MAIL FROM and FROM headers.
Marketer view
Marketer from Email Geeks says a colleague faced this error during a test message from a Prestashop install.
2023-05-22 - Email Geeks
Marketer view
Marketer from Email Geeks says they confirmed the domain was approved to send using their SMTP service, so the error seemed to be Prestashop-generated.
2023-05-22 - Email Geeks
Conclusion: ensuring seamless email flow
The "550 Mismatching sender domains" error in Prestashop can be challenging because it often indicates an internal validation issue rather than a generic SMTP rejection. By systematically checking your Prestashop email configuration, verifying SMTP credentials, and ensuring domain alignment, you can resolve most instances of this error. Remember that proper email setup is fundamental for maintaining good email deliverability and ensuring your messages reach the intended recipients.
If you continue to experience difficulties, consider enabling Prestashop's debug mode for more detailed error messages or consult a Prestashop developer. Tools for direct SMTP testing like swaks can also provide valuable insights into whether the problem originates from your Prestashop setup or the SMTP server itself. Always back up your Prestashop installation before making any significant changes to core files or database entries.
