Error message Unable to relay

Often emails are rejected by NoSpamProxy with the error message Unable to relay. However, the administrator usually does not notice this, since the rejected email was rejected due to an internal system rule and therefore, by default, there is no logging in message tracking.

Meaning of the error message

If an e-mail with this error message is rejected, the following reasons may be present:

  • For incoming emails, the "MAIL FROM" contains an email address from your own (corporate) domain. NoSpamProxy rejects this email because it does not expect any external emails sent from a corporate domain, unless the delivering server is listed as a corporate email server. This is an expected behavior.
  • In the case of outbound emails, there is no email address from your own (corporate) domain in the "MAIL FROM". NoSpamProxy rejects this email coming from within the system because it does not expect any internal emails containing unknown email domains. This is an expected behaviour, but can be adjusted if necessary.
  • For outbound emails, the "MAIL FROM" contains an email address from your own (corporate) email domain. NoSpamProxy rejects this internal email because it only allows internal emails that contain a corporate email domain if they are sent from registered email servers. This is an expected behaviour.
  • NoSpamProxy does not find a suitable rule for the email in question. This is especially true if the rules are configured to "Corporate email address" in the message flow and the internal email address is not known to NoSpamProxy, regardless of whether it is an inbound or outbound email.
  • For an inbound email, the recipient email domain is not defined as a separate email domain in NoSpamProxy.

Possible causes

  • If it is intended that the sending server is allowed to send emails from a corporate domain, be it from inside or outside, then this server must be listed as a "Corporate email server". This can be set in the NoSpamProxy Command Center under "Configuration > Email routing > Corporate email server".
  • If point 1 is configured correctly, it is possible that the set of rules in NoSpamProxy has not yet been configured correctly. The set of rules can be checked and corrected accordingly in the NoSpamProxy Command Center under "Configuration > Rules". Pay particular attention to the "Message Flow" tab in the rule in question. On this tab you determine which emails are to be processed by this rule.

NOTE: When creating new rules, make sure that they are correctly secured for the corresponding cases, so that an open relay is prevented!

How to make emails visible that have been rejected with Unable to relay.

Since emails with this error are not displayed in message tracking by default, it is possible to activate advanced monitoring.

  1. Go to Configuration > Advanced settings > Monitoring.
  2. Click Modify.
  3. Check the box Track invalid senders and recipients.
  4. Trigger a new delivery of the email.
  5. Check the message tracking again.

NOTE: This setting should only be activated for analysis purposes, otherwise there is a risk of the database of the Intranet Role (NoSpamProxyAddressSynchronization) becoming too large, especially when using SQL Express version, since the limit of currently 10GB will be reached quickly.