Suped

What causes a 550 Invalid Domain error from Virgilio and Libero and how can it be resolved?

8 Marketer opinions5 Expert opinions5 Technical articles2 Resources

Summary

The 550 Invalid Domain error from Virgilio and Libero is a multifaceted issue stemming from domain configuration, authentication, reputation, and potential temporary service disruptions. The error indicates that the receiving server deems the domain used in MAIL FROM, RCPT TO, or EHLO as invalid. Key causes include DMARC failures (often linked to aggressive DMARC handling by Libero), poor sender reputation (leading to blacklisting), incorrect or missing SPF/DKIM records, DNS issues (including the improper use of '.local'), misconfigured reverse DNS (PTR) records, invalid HELO/EHLO settings, and issues originating from the sending email service (e.g., Sendgrid). Solutions involve implementing strict sender authentication, managing domain reputation, validating DNS configurations, and considering the use of authenticated SMTP servers and confirmed opt-in processes.

Key findings

  • Root Cause: Receiving server considers sending domain invalid in MAIL FROM, RCPT TO, or EHLO.
  • DMARC Issues: DMARC failures, potentially exacerbated by Libero's aggressive policies, are a major cause.
  • Sender Reputation: Poor sender reputation (spam complaints, blacklisting) triggers rejections.
  • Authentication Failures: Missing or misconfigured SPF/DKIM records contribute to the problem.
  • DNS Problems: General DNS errors, including improper use of '.local', can lead to resolution failures.
  • PTR Records: Missing or improperly configured reverse DNS (PTR) records can cause rejection.
  • HELO/EHLO Configuration: Invalid or generic HELO/EHLO configurations may result in rejection.
  • External Service Issues: Problems with sending email services like Sendgrid (e.g., DNS issues) can cause temporary bounces.

Key considerations

  • Domain Validation: Ensure the sending domain is valid and correctly configured.
  • DMARC Implementation: Implement and monitor DMARC, ensuring SPF/DKIM alignment and addressing any failures.
  • Reputation Management: Actively manage sender reputation by minimizing spam complaints and avoiding blacklists.
  • Sender Authentication: Set up and verify SPF and DKIM records for all sending domains and services.
  • DNS Configuration: Ensure proper DNS configuration, including avoiding the use of '.local' for public-facing email.
  • PTR Record Setup: Configure a valid reverse DNS (PTR) record for your sending IP address.
  • HELO/EHLO Validation: Ensure the HELO/EHLO hostname is valid and matches the sending server's identity.
  • Service Monitoring: Monitor the status of your email sending service (e.g., Sendgrid) for any reported incidents.
  • SMTP Server: Consider using an authenticated SMTP server to improve email deliverability.
  • Opt-in Processes: Employ confirmed opt-in processes to minimize spam complaints and validate email addresses.

What email marketers say
8Marketer opinions

The 550 Invalid Domain error from Virgilio and Libero can stem from various issues related to the sender's domain configuration, authentication, and reputation. These include problems with DNS, DMARC policies, SPF/DKIM alignment, reverse DNS records (PTR), HELO/EHLO configuration, and the overall reputation of the sending domain. Additionally, temporary issues on the receiving mail server or problems with the sending email service (e.g., SendGrid) can also trigger this error. Proper configuration and maintenance of these aspects are essential for ensuring email deliverability.

Key opinions

  • Sendgrid Issue: A Sendgrid-related problem, potentially a DNS issue, may cause Invalid Domain errors (seen around 5/30-5/31).
  • Domain Configuration: Issues with the sender's domain configuration or reputation can lead to rejection by Virgilio and Libero.
  • DMARC Policy: A strict DMARC policy combined with SPF/DKIM alignment issues can result in Invalid Domain errors.
  • DNS Errors: General DNS errors, including an invalid domain name or other DNS-related problems, can cause this error.
  • Reverse DNS (PTR): Missing or misconfigured reverse DNS records (PTR) may lead to email rejection.
  • HELO/EHLO: Invalid or generic HELO/EHLO configurations can cause mail servers to reject connections.
  • Authentication Records: Incorrectly configured DKIM, SPF, and DMARC records cause email deliverability issues.

Key considerations

  • Check Sendgrid Status: If using Sendgrid, monitor their status page for any reported incidents that may affect email delivery.
  • Domain Reputation: Monitor and maintain a positive sender reputation to avoid being flagged by receiving mail servers.
  • DMARC Enforcement: Carefully configure DMARC policies, ensuring proper SPF/DKIM alignment to avoid unintended rejections.
  • DNS Configuration: Verify that all DNS records are correctly configured and resolving properly.
  • PTR Record Setup: Configure a valid reverse DNS record (PTR) for your sending IP address.
  • HELO/EHLO Settings: Ensure that your mail server's HELO/EHLO hostname is valid and consistent.
  • Sender Authentication: Verify that DKIM keys are correctly setup, SPF includes all sending servers/services, and a valid DMARC record is in place.
Marketer view

Email Marketer from Reddit explains that a strict DMARC policy (p=reject) on the sending domain, combined with SPF/DKIM alignment issues, can cause receiving servers like Virgilio and Libero to reject emails, resulting in an 'Invalid Domain' error.

June 2024 - Reddit
Marketer view

Email Marketer from EmailDeliveryWiki answers that common causes for bounce messages like Invalid Domain are: * The domain name is invalid. * There is a DNS error. * The recipient server has a security measure in place that rejects the email.

June 2024 - EmailDeliveryWiki
Marketer view

Email Marketer from Reddit explains that some mail servers check the HELO/EHLO domain name and may reject connections if it's invalid, generic, or doesn't match the sending server's hostname. Ensure your mail server is configured with a valid HELO/EHLO hostname.

August 2024 - Reddit
Marketer view

Email Marketer from Stack Overflow shares that the “Invalid Domain” bounce message often indicates an issue with the sender's domain configuration or reputation, leading the receiving server (like Virgilio/Libero) to reject the email.

February 2024 - Stack Overflow
Marketer view

Email Marketer from Mailhardener explains the importance of having all your DNS records set up correctly to ensure that you do not experience email acceptance issues, including: SPF, DKIM and DMARC.

January 2025 - Mailhardener
Marketer view

Email Marketer from EasyDMARC explains that it is important to ensure your DKIM key is correctly setup, your SPF includes all servers and services that you use, and to also ensure that you have a valid DMARC record setup that works for your domain.

May 2022 - EasyDMARC
Marketer view

Marketer from Email Geeks shares that they saw the same bounces from 5/30-5/31 and it was a Sendgrid-related problem, potentially a DNS issue, incident report: <https://status.sendgrid.com/incidents/yn928x2pvjqr>.

September 2022 - Email Geeks
Marketer view

Email Marketer from Digital Ocean explains the importance of a correctly configured reverse DNS record (PTR record) for your sending IP address. Some mail servers, including those used by Virgilio and Libero, may reject emails from servers without a valid PTR record or with a generic hostname.

February 2025 - Digital Ocean

What the experts say
5Expert opinions

The 550 Invalid Domain error from Virgilio and Libero indicates that the receiving server considers the domain used in the MAIL FROM, RCPT TO, or EHLO command to be invalid. This can be due to various reasons, including DMARC failures (possibly due to Libero's aggressive DMARC handling), poor sender reputation (leading to blacklisting or spam complaints), or issues with sender authentication. Implementing confirmed opt-in processes and ensuring proper SPF records are also crucial for resolving these errors.

Key opinions

  • Invalid Domain Cause: Virgilio and Libero think the domain in MAIL FROM, RCPT TO, or EHLO is invalid.
  • DMARC Failure: The error can be a response to DMARC failure, possibly due to Libero's overaggressive DMARC policies.
  • Sender Reputation: Poor sender reputation (spam complaints/blacklisting) can trigger the error even if the domain is technically valid.

Key considerations

  • Domain Validation: Ensure the domain used in MAIL FROM, RCPT TO, and EHLO is valid and properly configured.
  • SPF Configuration: Add SPF records for Sendgrid (or any other sending service) to authorize sending on behalf of the domain.
  • Reputation Management: Actively manage sender reputation to avoid being blacklisted or marked as spam.
  • Confirmed Opt-in: Implement confirmed opt-in processes to reduce spam complaints and ensure valid email addresses.
  • DMARC Monitoring: Monitor DMARC reports to identify and resolve authentication issues.
Expert view

Experts from Email Geeks explain that after DATA, an invalid domain error could be a weird response in the case of DMARC failure, which could be caused by Libero's overaggressive DMARC handling.

July 2023 - Email Geeks
Expert view

Expert from Word to the Wise explains that using confirmed opt-in processes can help resolve issues where users mark emails as spam and send emails with fake from addresses.

December 2021 - Word to the Wise
Expert view

Expert from Email Geeks explains that the 550 Invalid Domain error from Virgilio/Libero means they think the domain used in the preceding command (MAIL FROM, RCPT TO, maybe EHLO) isn't valid.

July 2021 - Email Geeks
Expert view

Expert from Spam Resource explains that if a sending domain has a poor reputation due to spam complaints or blacklisting, receiving servers like Virgilio and Libero may return a 550 Invalid Domain error, even if the domain itself is technically valid. Improving sender reputation is key to resolving this.

December 2022 - Spam Resource
Expert view

Expert from Email Geeks suggests getting the customer to add SPF for sendgrid to their domain to resolve DMARC issues.

December 2024 - Email Geeks

What the documentation says
5Technical articles

A 550 Invalid Domain error from Virgilio and Libero can be caused by several technical issues related to domain configuration and email authentication. Using the '.local' domain, failing DMARC checks (due to SPF/DKIM failures and quarantine/reject policies), and lacking proper sender authentication (SPF/DKIM) are common culprits. Additionally, a 550 error can indicate policy rejections, including domain validation failures. Using an authenticated SMTP server can help improve deliverability by ensuring proper domain validation and avoiding blacklisted IPs/domains.

Key findings

  • .local Domain: Using '.local' domain names can lead to resolution failures as they are reserved for Multicast DNS.
  • DMARC Failure: DMARC failure due to SPF/DKIM checks can lead to rejection, especially with quarantine/reject policies.
  • Sender Authentication: Missing or incorrect SPF/DKIM records can result in email rejection or spam marking.
  • 550 Error Meaning: A 550 error can indicate mailbox unavailability, non-existent user, or policy rejections like domain validation failures.
  • Authenticated SMTP: Using an authenticated SMTP server may improve delivery rates as the server validates and sends from non-blacklisted IPs/domains.

Key considerations

  • Avoid .local: Do not use '.local' domains for public internet-facing email.
  • DMARC Alignment: Ensure proper SPF and DKIM alignment to pass DMARC checks.
  • Authentication Setup: Implement and verify correct SPF and DKIM records for your sending domains.
  • Policy Review: Review and address any policy rejections related to domain validation.
  • SMTP Choice: Consider using an authenticated SMTP server to improve email deliverability.
Technical article

Documentation from AuthSMTP explains that using a authenticated SMTP server can improve mail delivery rates as the server will handle domain validations and ensure you aren't sending from a blacklisted IP/domain.

July 2023 - AuthSMTP
Technical article

Documentation from IETF explains that a 550 error typically indicates that the mailbox is unavailable or the user does not exist at the specified domain. However, it can also be used for various policy rejections, including domain validation failures.

September 2022 - RFC 5321
Technical article

Documentation from DMARC.org explains that a DMARC failure can occur if the email fails SPF or DKIM checks and the DMARC policy is set to quarantine or reject. This could lead to a rejection by the receiving mail server.

January 2023 - DMARC.org
Technical article

Documentation from RFC 6762 explains that the '.local' domain name is reserved for Multicast DNS and is not intended for use on the public internet. Using '.local' in domain names can lead to resolution failures.

April 2021 - RFC 6762
Technical article

Documentation from SendGrid explains that proper sender authentication, including SPF and DKIM, is crucial for email deliverability. Incorrect or missing authentication records can lead to emails being rejected or marked as spam.

January 2023 - SendGrid Documentation

Related resources
2Resources

Top 5 causes for email error 451 Temporary local problem
Top 5 causes for email error 451 Temporary local problem

Email error 451 Temporary local problem, is caused due to temporary mail relaying issues such as DNS errors, mail rate limits, etc. Here's how to fix them.

Bobcares
aria-pressed supports mixed? · Issue #1258 · w3c/aria · GitHub
aria-pressed supports mixed? · Issue #1258 · w3c/aria · GitHub

aria-pressed states: "A value of mixed means that the values of more than one item controlled by the button do not all share the same value. Examples of mixed-state buttons are described in the WAI...

GitHub

Related questions