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
8 marketer 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.
4 Sep 2021 - 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.
5 Jul 2022 - EmailDeliveryWiki
What the experts say
5 expert 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.
23 Jun 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.
16 Apr 2025 - Word to the Wise
What the documentation says
5 technical 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.
9 Dec 2021 - 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.
3 May 2024 - RFC 5321
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