To provide a more efficient filtering service we are making a change to the way that the
system handles identity locking. Currently the sending servers queue the messages that are submitted by a locked identity and are retrying the delivery until the message is either accepted or expired from the sending queue. No error or notification may be generated when messages are in the queue, which means that a locked identity may go undetected for some time if the lock notification message is missed.
Effective May 12, 2025 we will configure the filter to permanently reject messages submitted by a locked identity with a 5XX SMTP response code. In the most sender servers configuration, this will result in an non-delivery report (NDR) being generated, the text accompanying the error code will make it clear that there is an issue with the identity being used, and messages will not be queued.
This will improve overall protection against spam and unwanted email behaviors and avoid the potential for a large queue of undelivered messages building up.
To better protect our network against abuse, some extended filtering settings are being enforced at the system level. This might generates some of the submitted messages being quarantined. In case you need specific assistance in managing the outbound quarantine, you may contact the support team.
