| 1 | OK | |
| 2 | Unknown error | |
| 3 | Wrong syntax | Email address have wrong syntax |
| 6 | Wrong domain | Domain does not exits |
| 7 | Connection error | Cant connect to recipient mail server |
| 8 | Timeout | There is no reply in timeout period from recipient mail server |
| 10 | Socks proxy error | Cant connect to target host with socks proxy server or socks proxy error |
| 11 | Wrong mailbox | Mailbox does not exist |
| 12 | Mailbox temporary unavailable | |
| 13 | Refused by antispam system | |
| 14 | Too many parallel connections | Maximum parallel connections for your IP Address is reached |
| 15 | Rejected | Recipient is invalid or session is rejected |
