When attempting to release an email addressed to an external recipient from the Symantec Mail Security for Microsoft Exchange (SMSMSE) quarantine the item is never received by the recipient. If the quarantine view is refreshed, the item once again appears in the quarantine with the same quarantine ID and timestamp as prior to attempting to release.
550 5.7.1 Unable to relay
If a debugview log of the quarantine release attempt is generated per 'How to Obtain Debug Logs for Symantec Mail Security for Microsoft Exchange (SMSMSE)' the following error is observed:
00117582 9:08:17.790 AM  Error sending mail in the first attempt
00117583 9:08:17.790 AM  Code = 8004020f
00117584 9:08:17.790 AM  Code meaning = The event class for this subscription is in an invalid partition
00117585 9:08:17.790 AM  Source = (null)
00117586 9:08:17.790 AM  Description = The server rejected one or more recipient addresses. The server response was: 550 5.7.1 Unable to relay
The Original Recipient is an external recipient.
The Exchange server defined as the SMTP Server in SMSMSE Console under Monitors -> Notification settings does not accept messages address to external recipients via the SMTP protocol.
In order to allow SMSMSE to release to external recipients, we would recommend configuring a new receive connector whose scope includes only this Exchange server(IP), and allow relaying for that receive connector.
For details on how to accomplish this process, see 'Allow Anonymous Relay on a Receive Connector'