This article will help you navigate the various reasons why certain users may be excluded from email simulations, providing clarity on each situation.
If you're wondering why some of your users cannot receive emails and are marked by Symbol as "Undeliverable," you're not alone. Many administrators encounter this issue, and it can be frustrating when emails fail to reach their intended recipients. Understanding the underlying causes of these deliverability problems is essential for maintaining effective deliverability within your organization.
To assist you in diagnosing and resolving these issues, we have compiled a detailed table. This table categorizes the different error types associated with undeliverable emails, along with potential resolutions for each scenario. By reviewing this information, you can take informed steps to ensure that your users can receive simulation emails without interruption.
| Block Reason | Potential Resolution |
| The domain uses a catch-all address for role-based emails, which may not be monitored. | Emails within this error type are no longer blocked by Symbol Security. If you see this type of error, try re-validating the user(s) to confirm deliverability. |
| The email account that you tried to reach is inactive. | Confirm Google Workspace account is still active. |
| MailboxNotEnabledForRESTAPI, message: The mailbox is either inactive, soft-deleted, or is hosted on-premise. | Check user license is valid, Check mailbox status is active and not soft deleted, Check if user license is On-Prem if so migrate to Exchange Online |
| Gmail has detected that this message is likely 550-5.7.1 suspicious due to the very low reputation of the sending IP address. | Ensure Symbol’s IPs and domains are fully whitelisted across your email filters, firewalls, and any third-party security tools. Due to recent and upcoming changes by Google, this type of rejection may continue even after basic whitelisting. As a result, we recommend enabling Symbol Inbox Delivery (SID) as the most reliable solution to ensure consistent email delivery to user inboxes. |
| The recipient's email address does not exist. | Double-check for typos in email address, confirm email address is valid and active, if using director (MSFT, Google, etc.) verify account is properly synced and licensed, ensure user list is updated. |
| The recipient's server temporarily rejected the email. Please try again later. | Ensure Symbol’s IPs and domains are fully whitelisted across your email filters, firewalls, and any third-party security tools. |
| The recipient's email server blocked this message due to strict anti-spam filters. | |
| The connection was forcibly closed by the recipient's mail server. | |
| Unable to send email: User in suppression list. | Email address has been placed on suppression list by Symbol's ESP due to hard bounce. Ensure Symbol’s IPs and domains are fully whitelisted across your email filters, firewalls, and any third-party security tools. Then notify Symbol Support when whitelisting has been confirmed so accounts can be removed from Suppression list and email validation test can reinitialized. |
|
This email address is on a global suppression list and cannot receive messages.
|
|
| This domain or email address does not accept incoming mail. | Check if domain is set up with MX records, ensure email address is not send-only or outbound-only account, ensure domain configured to receive emails, ensure security policy does not block all external inbound emails |
| The domain does not have valid DNS records for email delivery. | Check for valid MX records, Ensure domain is active, Correct DNS configuration. |
If you have any questions regarding these types of roles or you're seeing a non-listed error type, please don't hesitate to reach out to us for further assistance. We are here to help you!