If an email you send to an IONOS customer cannot be delivered, you will receive an email with a status code. This status code informs you about the exact reasons why the message was undeliverable. The following overview lists these status codes and shows you how to eliminate the causes.
- The following status messages concern emails that are sent to IONOS-hosted email addresses. Status messages for emails that you, as an IONOS customer, send to others are dealt with in the Help Center articles Error messages for undeliverable emails and Bounced Email Due to Alleged Spam / IONOS Mail Server on a Blacklist.
- Please note that the email problems and their solutions specifically describe the situation at IONOS. Other email service providers may have different settings.
- If you are not the operator of the sending mail server yourself, please contact the administrator or customer service of the operator for administration and configuration settings.
421 Rejected due to policy violations
Due to a poor delivery rate by sending to too many non-existent email addresses, the IP address of your email server is blocked from sending email to IONOS customers.
Your sender address has been reported as a spam sender in the past.
Review and clean up your email sending list by deleting inactive and outdated recipient addresses. Restart the email dispatch at a later time.
450 Rejected due to policy violations
The delivery of emails was temporarily delayed due to a constantly changing HELO/EHLO entry of your email server.
Due to a poor delivery rate by sending to too many non-existent email addresses, the IP address of your email server is blocked for emails to IONOS customers.
Changing HELO/EHLO entries in the SMTP dialog can indicate an infected system that is being misused by a virus to send spam. Check and clean up your system with a virus scanner. Restart the email dispatch at a later time.
Check and clean up your email dispatch list by deleting inactive and outdated recipient addresses. Restart the email sending process at a later time.
550 Syntax error in parameters or arguments
Due to a faulty configuration, the receipt of emails is rejected.
Check with our recommendations whether your server is configured correctly.
550 Reject due to policy restrictions
The sender domain you are using is known as spam domain.
The HELO/EHLO entry of the dispatch server does not correspond to a fully qualified domain name (FQDN).
Check with a blacklist provider such as Spamhaus whether your address is listed as a spam sender. Apply for a deletion of the entry.
Assign a fully qualified domain name (FQDN) to your mail system.
If the error still occurs, please contact us.
550 Administrative reject
For administrative reasons, email delivery is not allowed.
Contact us to have the problem checked.
550 Invalid DNS MX or A/AAAA resource record
The sender domain of the email server you are using is not configured in the domain name service (DNS) in accordance with RFC.
Check the following DNS problems and correct them if necessary:
- Neither an A nor an MX record is configured in the DNS for the sender domain.
- The MX record points to a domain name that cannot be resolved.
- The MX record refers directly to an IP address.
- The MX server does not have a valid A record but only a CNAME record
For more information about your DNS configuration, for example, contact http://www.intodns.com.
550 Sender address has null MX
The domain from which you send email has a configured No Service MX record (zero MX). The IONOS SMTP recipient rejects such emails.
Delete the No Service MX entry in the DNS settings of your domain. For more information about a No Service MX entry, see RFC 7505.
554 Bad DNS PTR resource record
Email from your email server has been rejected because the PTR resource record (PTR-RR) of your IP address does not comply with IONOS policy.
Switch from a dynamically assigned IP address to a fixed IP address.
Verify that the PTR-RR is the default generic entry of your provider. Assign your email server its own full domain name (FQDN).
554 Reject due to policy restrictions
The email was rejected as it violates IONOS policy. The sending server is mostly sending spam messages.
Contact us IONOS to have the facts of the case examined.
554 Transaction failed, reject due to policy restrictions
The email client must meet the following criteria:
- The header lines of the email must contain exactly one valid "Date" line according to RFC 2822.
- The following header lines may only exist once: From, Sender, To, CC, Subject
- The header lines mentioned must be syntactically correct
Note: The To and CC lines can contain multiple recipients.
In accordance with the recommendations from RFC7103, incorrect messages are not automatically corrected by IONOS, otherwise DKIM signatures become invalid. For more information about DKIM signatures, see the IONOS article Configuring DMARC Records for a Domain.
556 Recipient address has null MX
The domain to which you wanted to send an email has a configured No Service MX entry (null MX). This means that the domain can neither receive nor send email.
Contact the administrator of the receiving domain to have this entry checked. For more information about a No Service MX entry, see RFC 7505.
Status code not listed
Your status code was not listed or you need further assistance?