The following is a description of the outbound message bounce types and categories reported to Hurricane Server plugins.
Hard - Your message encountered an error and was not delivered. Future messages to this recipient will fail. (i.e. user unknown, mailbox not found, etc.)
Soft - Your message encountered an error and was not delivered. Future messages to this recipient may succeed. (i.e. mailbox full, account disabled, exceeds quota, out of disk space, relaying denied)
Challenge - Your message was blocked and further action is necessary to deliver your message. Typically these bounces are sent from spam filters which have quarantined your message, but will deliver it if you follow the instructions in the bounce.
Spam - Your message has been identified as spam and was blocked.
Virus - Your message contained a virus and was blocked.
Blocked - Other Your message was blocked for an unknown or general reason.
Transient - Your message encountered an error, but the error condition may be temporary and delivery attempts are still being made. (i.e. unable to connect to recipient's mail server)
Auto-reply - The bounce is an auto-reply. (i.e. out of office, vacation)
Subscribe - The bounce is a subscribe request. (i.e. someone wants to join a mailing list)
Unsubscribe - The bounce is an unsubscribe request. (i.e. someone wants to be taken off of a mailing list)
Address Change - The bounce is an address change notification.
Modified - Your message was modified prior to delivery. (i.e. illegal attachment removed)
Delivered - Your message was delivered. (i.e. delivery status notification reply from recipient's server indicating that your message was delivered)
Custom - Reserved for future use
Unknown - The category of the bounce could not be determined.