There are several message history events that could be shown for a given message. Below is a brief description of each history event type.


Send - The most common event type this is registered when the message is sent to the user.


Deferral - Typically due to a minor email sending outage, this message has been queued to be sent later.


Hard Bounce - This is a permanent error where a mailbox does not exist and the message will never be able to be delivered.


Soft Bounce - This is a temporary error like the recipient email address has a full mailbox. Message delivery will be attempted again.


Open - When a user opens to view your email message. It's important to note that not every email client supports this functionality.


Click - A user clicked on a URL within your email message.


Spam - The user has reported this message as spam. 


Unsub - The user has requested to be unsubscribed from future emails.


Reject - The recipient email server has rejected the email message. There are many reasons for a possible rejection.