在做email营销时日志中会返回一些状态码来告知邮件发送是否成功，类似访问网站时header中的状态码，404表示页面不存在等等。发送邮件的状态码2.0.0则表示成功投递，而我们常说的Soft Bounce和Hard Bounce状态码总结如下：
Bounce code |
Bounce type |
Description |
| 5.0.0 | Hard | Address does not exist |
| 5.1.0 | Hard | Other address status |
| 5.1.1 | Hard | Bad destination mailbox address |
| 5.1.2 | Hard | Bad destination system address |
| 5.1.3 | Hard | Bad destination mailbox address syntax |
| 5.1.4 | Hard | Destination mailbox address ambiguous |
| 5.1.5 | Hard | Destination mailbox address valid |
| 5.1.6 | Hard | Mailbox has moved |
| 5.1.7 | Hard | Bad sender’s mailbox address syntax |
| 5.1.8 | Hard | Bad sender’s system address |
| 5.2.0 | Soft | Other or undefined mailbox status |
| 5.2.1 | Soft | Mailbox disabled, not accepting messages |
| 5.2.2 | Soft | Mailbox full |
| 5.2.3 | Hard | Message length exceeds administrative limit. |
| 5.2.4 | Hard | Mailing list expansion problem |
| 5.3.0 | Hard | Other or undefined mail system status |
| 5.3.1 | Soft | Mail system full |
| 5.3.2 | Hard | System not accepting network messages |
| 5.3.3 | Hard | System not capable of selected features |
| 5.3.4 | Hard | Message too big for system |
| 5.4.0 | Hard | Other or undefined network or routing status |
| 5.4.1 | Hard | No answer from host |
| 5.4.2 | Hard | Bad connection |
| 5.4.3 | Hard | Routing server failure |
| 5.4.4 | Hard | Unable to route |
| 5.4.5 | Soft | Network congestion |
| 5.4.6 | Hard | Routing loop detected |
| 5.4.7 | Hard | Delivery time expired |
| 5.5.0 | Hard | Other or undefined protocol status |
| 5.5.1 | Hard | Invalid command |
| 5.5.2 | Hard | Syntax error |
| 5.5.3 | Soft | Too many recipients |
| 5.5.4 | Hard | Invalid command arguments |
| 5.5.5 | Hard | Wrong protocol version |
| 5.6.0 | Hard | Other or undefined media error |
| 5.6.1 | Hard | Media not supported |
| 5.6.2 | Hard | Conversion required and prohibited |
| 5.6.3 | Hard | Conversion required but not supported |
| 5.6.4 | Hard | Conversion with loss performed |
| 5.6.5 | Hard | Conversion failed |
| 5.7.0 | Hard | Other or undefined security status |
| 5.7.1 | Hard | Delivery not authorized, message refused |
| 5.7.2 | Hard | Mailing list expansion prohibited |
| 5.7.3 | Hard | Security conversion required but not possible |
| 5.7.4 | Hard | Security features not supported |
| 5.7.5 | Hard | Cryptographic failure |
| 5.7.6 | Hard | Cryptographic algorithm not supported |
| 5.7.7 | Hard | Message integrity failure |
| 9.1.1 | Hard | Hard bounce with no bounce code found. It could be an invalid email or rejected email from your mail server (such as from a sending limit). |
