| | OK CODES |
| 0 | OK and mail has been downloaded |
| 1 | OK and no mail waiting in the server |
| 2..9 | Reserved for other OK codes |
| | ERROR CODES |
| 10 | Reserved code, not used |
| 11 | Generic command line error |
| 12 | Winsock setup or version error |
| 13 | XATRN supported or selected authentication types are not supported by the ATRN server |
| 14 | Authentication refused by XATRN server (invalid username or pwd ?) |
| 15 | cannot resolve hostname of ATRNserver [gethostbyname() failed] |
| 16 | cannot resolve hostname of SMTPserver [gethostbyname() failed] |
| 17 | cannot open TCP connection to ATRN server |
| 18 | cannot open TCP connection to SMTP server |
| 19 | SMTP protocol error or timeout (with XATRN or SMTP server) |
| 20 | Internal encoding error |