As i mentioned in my last post SMTP commands are answered with numeric responses. Here I have included some common SMTP server response codes and what they mean. If at any stage in an SMTP transaction there is an error, it will have a unique code assigned to it so the user can hopefully determine why it has happened. However the response codes are not always errors, SMTP will also output a success code.
The first digit of the response denotes whether it is good, incomplete or simply bad.
2 = success – 4 = temporary failure 5 = permanent failure
- 211 – System status or system help reply
- 214 – Help message
- 220 – The SMTP service is ready
- 221 – SMTP is closing the transmision channel
- 250 – The command has been completed
- 354 – OK to transmit message
- 450 – Command can not be completed because mailbox is busy.
- 451 – Command has been aborted because of an error
- 452 – Command has been aborted because the receiving server is out of disk space
- 500 – Syntax Error
- 550 – Mailbox is not available or doesnt exist
- 552 – Command was aborted because the recipient exceeded their storage quota
- 554 – The transaction has failed.
- 556 – Transaction failed due to bad weather! (only joking)