A ​Response​ is a message that does not reach the contact. The message is either sorted out during sendout or rejected by the receiving MTA. An email campaign can generate many different kinds of responses.

Responses contain information about why a message was rejected or not delivered. To make it easier to handle responses, Mapp Engage analyses and categorizes responses into three general ​Response Classes​. Within the three response classes, responses are sorted into seven detailed ​Response Categories​ .

Related Topics​

Deactivation (tab)​

Response Class​

The response class provides general information about why the delivery of a message was not successful.

Response Class





Generated before sendout

Generated by Mapp Engage

This class describes messages that Mapp Engage identifies as undeliverable and does not attempt to send out. Skipped messages never leave the Mapp infrastructure. The Mapp server does not attempt to contact the address.

Possible reasons for a skip include:

  • The address was on an system-wide blacklist or Robinson list.

  • The contact reached the system-wide message limit.

  • The contact information necessary for the selected type of message was not available.
    For more information, see Skipped Messages (tab)​.


Generated after sendout, but before arrival in the inbox

Generated by the MTA

This class describes messages that are sent out by Mapp Engage, but not accepted by the receiving Mail Transfer Agent (MTA). The receiving Mail Transfer Agent forwards a notification to Mapp Engage that a message was refused.

Bounced messages never arrive in the contact's inbox.

Sometimes the bounce notification is an error. Mapp Engage can identify such errors based on verifiable user activity (for example, an open or a click). In this case, the message is declassified as a bounce, and is not included in the total number of bounces for the message.

Additionally, the Email Experience Council (eec) divides bounces into ​Hard​ and ​Soft Bounces​.

  • Hard Bounces: Delivery failures due to permanent conditions such as a non-existent email address.

  • Soft Bounces: Delivery failures due to temporary conditions such as a full inbox.


Generated after arrival

Generated by the Contact

This class describes messages that are delivered to the inbox of a recipient. However, the contact generates a response, which is then sent back to Mapp Engage.

Examples include:

  • Out of office replies.

  • Spam complaints.

Both the Internet Service Provider and recipients can generate ​Feedback​ responses.

Hint: Although automatic responses such as Out of Office replies are classified as ​Feedback​, they are not displayed on the ​Deactivation​ tab. Automated responses usually indicate a temporary condition on the part of the recipient and are not grounds for deactivation.

Response Category​

Response categories provides more detailed information about the response. This information helps determine how to correctly handle deactivation.

For more information, see Deactivation (tab)​.

Response Category


Response Class

Communication Failure

This delivery failure response is generated by issues such as a temporary interruption of communication with the MTA.



This delivery failure response is generated if the domain of the email address does not exist (for example, ohtmail.com instead of hotmail.com) or the domain name could not be resolved due to DNS problems at the ISP.

Spam Complaint

This message delivery response is created when either the message recipient or their Internet Service Provider (ISP) report a message as spam (for example, when a recipient clicks the spam button in their email application). The settings for the ​Spam Complaint​ category cannot be changed. As soon as a complaint is registered, the recipient who reported the message as spam is automatically deactivated in the group.



This delivery failure response is generated when an address no longer exists or if the email account is not active.



The contacts in this category are deactivated due to responses caused by issues such as a full inbox or a lack of available disk space. Since these issues can be temporary, the system keeps trying to deliver the message every six hours. The message sits in the queue for two days. If delivery fails after this time, the message is counted as as a permanent failure transient bounce.


This delivery failure response is used when the exact cause of the delivery failure cannot be determined. Although the reason that the message generated a response is unclear, message responses in the ​Unknown​ category are classified as ​Bounces​.


This delivery failure response is caused when either the receiving Mail Transfer Agent (MTA) or the recipient refuses to Mapp Engage delivery of a message (for example, because the sending address appears on a blocklist). Many Internet Service Providers (ISPs) block email from IP addresses or domains that have been reported for spam, viruses or content that violates email policies or spam filters.