After setting up a new Mailbox in your organization, Emails sent from external senders to the new Mailbox are rejected or dropped by the Symantec Messaging Gateway (SMG).
The issue you are seeing matches all of the following:
- A Recipient Validation source is setup on the SMG with Invalid Recipient Handling configuration set to "Reject invalid recipients" or "Drop invalid recipients". - Emails to other mailboxes at the same domain can be received without the same problem. - The Message Audit Logs of the SMG shows that Emails to the new Mailbox triggered the defined action in the Invalid Recipient Handling configuration of the SMG. - By going into the Recipient Validation source's configuration (found under Administration -> Directory Integration), you have been able to verify that the new mailbox can be found in the "Recipient Validation Query" page where you have tested the mailbox's existence.
Emails to the new mailbox may be rejected with the following error (if the Recipient Validation configuration is set to "Reject invalid recipients")
554 Recipient address rejected: User unknown
This is the expected behaviour of the Messaging Gateway in a situation where an Email was received by the Symantec Messaging Gateway intended for the new mailbox, at a time when the mailbox had not yet fully been created on the Recipient Validation source.
This will result in the Messaging Gateway caching a "mailbox doesn't exist" result for the new mailbox, which the Recipient Validation module will then check when any subsequent Emails are received until the Messaging Gateway's Directory Source cache TTL (Time To Live) has expired.
Once the cache expires for the query, the Messaging Gateway will perform a new query to Recipient Validation source when a new Email arrives for the mailbox, resulting in the mailbox being found (allowing the Email to pass through this check).
Clearing the Directory Source's lookup cache will force the Messaging Gateway to perform a new Recipient Validation lookup upon each Email being received. This will result in the Mailbox being found and new query cache being stored for the mailbox (along with every other mailbox the Messaging Gateway receives Email for).
PLEASE NOTE: If the Directory Source cache is not cleared, this behaviour will generally resolve itself once the TTL (Time to Live) of the Messaging Gateway's Directory Source cache has been reached, by default this will be between 12 and 36 hours. The caching settings of the Directory Source can be found in the Advanced configuration of the source as "Minimum cache TTL" and "Maximum cache TTL".
Imported Document ID: TECH173973
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