Use this table to understand common email delivery errors and what they mean.
Error | Description and information |
452 4.2.2 The email account that you tried to reach is over quota | The client’s mailbox is full. Ask the client to clear space or contact their email provider. |
550 5.0 recipient or address rejected | The recipient server is rejecting your emails, most likely because your address is blocked. Ask the client to whitelist ddslive.com.au, or if sending from your own domain via Office 365, ensure the sending address is whitelisted. |
550 5.1.1 recipient rejected. Recipient does not exist | The email address is invalid or does not exist in the destination domain. This may be caused by a typo or the recipient’s server being misconfigured. |
550 5.2.1 recipient rejected. Mailbox suspended | The email address exists, but the account has been suspended or blocked. Ask the client to contact their email provider. |
550 5.1 | The recipient server is rejecting emails from your domain. This is usually caused by a DNS configuration issue. |
550.5.7.0 Message Size Violation | The email contains an attachment exceeding the recipient’s size limit. Reduce file size before resending. |
550 5.7.1 Connection refused | The recipient server is blocking the connection. Ask the client to whitelist ddslive.com.au or your sending address (if using the Office 365 API). |
550 5.7.1 Service unavailable | The client host is blocked by the Customer Block List. Ask the client to whitelist ddslive.com.au or your sending address (if using the Office 365 API). |
550 5.7.1 DDNS says spammer, 20191030-1 dodgyfrom | Your email or domain is being flagged as suspicious. Ask the client to whitelist ddslive.com.au or your Office 365 API sending address. |
550 5.1.10 RESOLVER.ADR.RecipientNotFound | Occurs when a user was created in Office 365 but the on‑premises Exchange environment has no corresponding object. Queries for that SMTP address fail until directory synchronisation is fixed. |
550 Denied By Policy | Security software has blocked outbound emails, often to stop automated guessing of email addresses. Ask the client to whitelist ddslive.com.au or your Office 365 API sending address. |
Undeliverable (MailGuard, MailControl) | The message could not be delivered after repeated attempts. A connection to the remote server could not be established. The client may need their IT team to release the email from their system. Also advise them to whitelist ddslive.com.au or your sending address. |
550 Badly formed From: header | Contact [email protected] |
550 permanent failure for one or more recipients | Contact [email protected] |