Mail with the Error Main Class have not been delivered successfully due to some kind of issue accessing, verifying or processing the message. Messages caught in this state will be retried.
Messages with a Main Class of Error can have any of the following Sub Classes:
Sub Class:
antivirus-unavailable
A temporary error prevented scanning of the message through anti-virus systems, so the message was temporarily rejected and will be retried later.
database-unavailable
A temporary error occurred accessing the database. The message will be retried later.
memory
A temporary error occurred while processing the message, and it will be retried later.
database-crash
A temporary error occurred accessing the database. The message will be retried later.
unknown
An error occurred processing the message; it will be retried later.
verification-fail
An issue prevented verifying that the recipient domain was known to the cluster.
verification-crash
An issue prevented verifying that the recipient domain was known to the cluster.