| Delivered | Not applicable | Successful delivery of email to recipient. |
| Skipped | Not sent: Blocked by mail filter | The sending rate is not accurate or is too high (similar email messages are being sent too rapidly). |
| Skipped | Not sent: Specific address(es) recently bounced | The email was not sent because the recipient address appears on the Bounced Email Addresses list. |
| Skipped | Not sent: No MX or A for domain | The email was not sent because there is no DNS record (an MX or an A record) for the domain. |
| Undelivered | Permanent Failure: Delivery not authorized, message refused | The sender is not authorized to send to the destination. This can be the result of per-host or per-recipient filtering. |
| Undelivered | Permanent Failure: No answer from host | The outbound connection attempt was not answered. |
| Undelivered | Permanent Failure: Bad destination mailbox address | The mailbox specified in the address does not exist. |
| Undelivered | Permanent Failure: Unable to route | The mail system was unable to determine the next hop for the message because the necessary routing information was unavailable from the directory server. |
| Undelivered | Permanent Failure: Mailbox disabled, not accepting messages | The mailbox exists, but is not accepting mess |