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Relay errors when Exchange or Messaging Gateway changes recipent during inbound delivery


Article ID: 175921


Updated On:


Messaging Gateway


  • Exchange server is set to send email from one box to another box on another domain
  • Inbound email to the Symantec Messaging Gateway (SMG) domain is getting relay errors.
  • Message Audit Log shows inbound queue, original recipient is mailbox for local domain, and actual recipent is mailbox for a non-local domain

5.7.1 smtp; 550 5.7.1 Unable to relay


Microsoft Exchange

Messaging Gateway


This is caused when SMG does not have an explicit delivery route for the non-local domain.

By default, SMG always routes email in the inbound queue to a local server. When the recipient is changed to the non-local mailbox, the SMG does not have a hardset routing rule, and attempts to deliver the mail locally, which fails. The local Exchange server does not accept email for the non-local domain, and blocks the email relay.


Add a delivery routing to Domains in SMG

  1. Go to Protocols > SMTP > Domains in SMG.
  2. Look for the non-local domain.
  3. If the non-local domain is listed, then ensure the routing under the Delivery tab is set to MX Lookup.
  4. If the non-local domain is not listed, then:
    1. add the domain by clicking the Add button
    2. uncheck Local domain under the Acceptance tab
    3. under the Delivery tab, select ""
    4. Select "MX Lookup"
    5. Click Save

This will make sure that any email that passes into the Delivery queue for the non-local domain gets routed correctly. This setting will override the default inbound routing for the non-local domain.


  • These instructions assume that standard mail routing is allowed via MX Lookup on the SMG. If the internal network must route through a different host, use that host instead of MX Lookup.
  • If further questions need to be answered, please contact Enterprise Support. Symantec Enterprise Support is limited in assistance of routing issue on internal networks, but will but a "best effort" to assist.