551 5.4.6 Private/Loopback Address Bounce received with PBE-Z
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551 5.4.6 Private/Loopback Address Bounce received with PBE-Z


Article ID: 163486


Updated On:


Email Security.cloud


Your Users send encrypted emails using Symantec Policy Based Encryption-Z (PBE-Z). Shortly after the user receives a non delivery receipt (NDR) or bounced email stating delivery failed to the intended recipient.

Delivery has failed to these recipients or groups:
[email protected]***-trusted.zixroute.com
A problem occurred during the delivery of this message. Please try to resend the message later. If the problem continues, contact your helpdesk.

Diagnostic information for administrators:
Generating server: server-**.bemta-**.messagelabs.com
[email protected]***-trusted.zixroute.com
Remote Server returned '< #5.4.6 smtp; 551 5.4.6 [internal] Private/Loopback Address>'


The inbound route configured for the registered subdomain for the PBE-Z service has been incorrectly configured. When subscribed to the PBE-Z service, 2 subdomains will be added to your account.

  • encryptz-**.yourdomain.com (where ** is either US or EU depending on your region and yourdomain.com replaced by your organization's domain)
  • zixvpm.yourdomain.com

Each of these subdomains will be configured with a custom inbound route unique to them. This is to ensure, once the email triggers your encryption policy, that it is routed to the proper encryption server and processed for delivery. these routes will be the following, depending on your region.

North America:

encryptz-us.yourdomain.com: pc02.z118.zixworks.com
zixvpm.yourdomain.com: pc01.z118.zixworks.com


encrytz-eu.yourdomain.com: pc02.z201.zixworks.com
zixvpm.yourdomain.com: pc01.z201.zixworks.com

If the pc01 route is configured to be used for the encryptz subdomain, the bounce back stated above will be received by the sender.


The inbound route for the encryptz subdomain must be corrected for proper email encryption routing. To do this, follow the below steps:

To add a custom route to a domain

  1. Select Services > Email Services > Inbound Routes.

  2. In the Custom Routes section, click Manage Settings against the domain you want to add the custom route to.

  3. Click Add and Check New Custom.

  4. Enter the route based on your encryptz subdomain as describe above in the cause section.

  5. Click Add.

Please allow up to 1 hour for propagation to complete before the new route takes effect.