Common external Spam Filtering Error Codes

Products

• Email Security.cloud

Issue/Introduction

This article describes common errors observed when attempting to deliver an email to an external recipient's (non-customer) mail server. These errors would be generated by the recipient's side and their Spam Filtering/Content Control gateway.

The list of errors contains the following error messages but it is not limited only to them:

• 550 "5.7.0" Mail relay denied
• 550 5.7.1 Message rejected as spam by Content Filtering
• 550 Connection refused
• 550 Message contained unsafe content (Heuristics.Phishing.Email.SpoofedDomain)
• 550 Permission denied
• 551 Sender is on domain's blacklist
• 5.7.1 Recipient not authorized, your IP has been found on a block list
• 5.7.1 Message Rejected as spam by Content Filter
• 554 Rejected due to banned content
• 554 Rejected due to spam content

Environment

Email Security.cloud

Cause

These errors are generated by the recipient's mail server or their local security gateway. Email Security.cloud has successfully attempted delivery, but the destination server has issued a permanent rejection based on its own local policies or content filtering rules.

Resolution

Email Security.cloud acts as the sender and the receiving server is the one issuing these codes. You can find these codes in the Track and Trace or Email Delivery logs within the portal.

Resolution Steps:

1. Identify the specific error code in the Track and Trace logs.
2. Confirm that the status shows a successful handoff to the recipient's IP.
3. Contact the recipient through an alternative channel.
4. Request that the recipient's IT team whitelist your domain or adjust their heuristic filter settings.