Google Workspace, like all other email service providers, uses a Simple Mail Transfer Protocol (SMTP) to exchange messages with other servers. SMTP uses a standardized set of reply codes described in RFC 5321, where error code 550 means “Requested action not taken: mailbox unavailable.”
SMTP error code 550 is very common because it covers a broad range of issues related to email rejection, often due to security, delivery, or configuration reasons. Some of the possible reasons are:
On the other hand, some of the common issues that DO NOT cause SMTP error 550 include:
The full list can be found in the official Google Workspace documentation. As an email administrator, you can face the "550 Permanent Failure for One or More Recipients" issue from both the sending and the recipient sides. Therefore, you should understand the troubleshooting cases in both cases.
In case users in your organization receive a "550 Permanent Failure for One or More Recipients" error, the first thing you need to do is identify the issue scope – is it organization-wide or isolated to specific users or emails? If multiple users across the organization are receiving this error for most or all outgoing emails, it suggests a larger, systemic issue. This may point to a misconfiguration at the domain level, affecting every email sent from the organization. If only a few users or specific messages are affected, the problem is likely more localized. It may be due to specific recipients, individual sender configurations, or content in specific emails that trigger spam or policy filters on the recipient’s server.
In case the problem is on the organization level, most likely, messages are blocked for security reasons because the domain is not configured correctly. The following troubleshooting steps must be taken:
1. Go to the Google Admin Toolbox at https://toolbox.googleapps.com/apps/main/.
2. Select Check MX.
Google Admin Toolbox offers tools like 'Check MX' to verify DNS configurations and debug browser issues, helping troubleshoot Google Workspace services.
3. Enter your domain name and press Run Checks!
The Google Admin Toolbox Check MX tool interface allows users to input a domain name and run checks on MX and DKIM settings. It includes a clear "Run Checks!" button for quick verification.
4. Review the test output. Each finding has a link to the respective help center article, which you can use to resolve the issue.
The Google Admin Toolbox Check MX results highlight issues like missing mail server, DKIM, DMARC, SPF, and MTA-STS records. It also confirms compliance for NS servers and TXT records.
SMTP error code 550 is particularly common in SMTP relay scenarios because it is often used to indicate that a server is refusing to relay an email due to security, configuration, or policy restrictions. In case you use Google Workspace to send messages from printers or applications using the SMTP-relay feature and face this issue, perform the following troubleshooting steps:
1. Go to Google Admin Console at admin.google.com
2. Navigate to Apps > Google Workspace > Gmail on the right side.
The Google Admin Console displays the navigation to Gmail settings under Apps > Google Workspace. It shows Gmail status as "ON" for everyone, indicating active service.
3. Scroll down and select Routing.
Google Admin Console displays Gmail settings, including End User Access, Spam, Compliance, and Routing options, allowing administrators to configure features.
4. On the Routing page, scroll down to SMTP relay service and select Configure.
The Google Admin Console displays configuration options for Non-Gmail mailbox routing, alternate secure routes, and SMTP relay service. Administrators can manage outbound mail settings using the "Configure" button.
5. Review the configuration of the SMTP relay. Ensure that the IP address of the printer or application is allowed to send messages. Double-check the authentication and TLS configurations; they must be identical in Google Workspace and the printer/application.
Google Admin Console SMTP relay settings include options for allowed senders and IP-based authentication. Encryption options like TLS can also be configured.
To troubleshoot errors returned for specific emails or users, follow these steps:
If possible, rephrase the message to make it appear less suspicious.
When a Google Workspace administrator encounters SMTP error 550 for incoming messages, it generally means that emails sent to the organization are being rejected by Google’s mail servers. In this scenario, the following troubleshooting steps could help:
1. Check the recipient’s email account. First of all, ensure it exists within your organization. Also, one of the reasons for the "550 Permanent Failure for One or More Recipients" error message is the recipient’s account being disabled. To check the user status, perform the following steps:
a. Go to Google Admin Console at admin.google.com
b. Navigate to Directory > Users on the left pane.
Google Admin Console displays the Directory > Users section for managing users in organizational units. Admins can search and filter users by organizational units.
c. Find the problematic user in the list. Look for the Status column, where the suspension status is shown.
Google Admin Console shows the user management section with details of active and suspended accounts. Admins can view status, email, and last login activity.
d. If the user account is suspended, go to More Options>Reactivate.
The Google Admin Console user management section displays actions like reactivating suspended users, resetting passwords, or deleting accounts. Admins can manage user settings efficiently.
e. Confirm the action by selecting Reactivate.
The Google Admin Console displays a confirmation prompt for reactivating a suspended user. Admins can choose to proceed with reactivation or cancel the action.
2. Contact the sender and ask to review the message. Google Workspace can only process messages that are compliant with the RFC5322 standard, which also follows the best practices for email hygiene.
3. Contact the sender's email administrator and ask to review their domain configuration. To ensure deliverability, the sending server must follow the industry's best practices and have PTR, SPF, MX, and other records properly configured. For example, if the sender’s IP address does not have a DNS pointer record (PTR) or the forward DNS entry does not point to the sending IP, the message will return error code 550. More details can be found on the Google Workspace help page.
SMTP error 550 is a general error code indicating that an email has been rejected by the recipient’s email server. It is often confusing because it may be caused by many different reasons, such as mailbox unavailability, SMTP-relay restrictions, recipient’s security policies, and others. For Google Workspace administrators, understanding the underlying causes of this error is essential for efficient troubleshooting. By methodically investigating both outgoing and incoming issues, administrators can often isolate the specific cause and implement corrective measures, keeping the email service highly available and reliable.
