What causes a 550 Invalid Domain error from Virgilio and Libero and how can it be resolved?
Summary
What email marketers say8Marketer opinions
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.
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.
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.
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.
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.
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.
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>.
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.
What the experts say5Expert opinions
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.
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.
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.
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.
Expert from Email Geeks suggests getting the customer to add SPF for sendgrid to their domain to resolve DMARC issues.
What the documentation says5Technical articles
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.
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.
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.
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.
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.