Here is a full list of the SMTP error codes you may encounter;
Error Code |
Error Type |
Description |
| 0x800CCC60 | SMTP_RESPONSE_ERROR | Invalid response |
| 0x800CCC61 | SMTP_UNKNOWN_RESPONSE_CODE | Unknown error code |
| 0x800CCC62 | SMTP_500_SYNTAX_ERROR | Syntax error returned |
| 0x800CCC63 | SMTP_501_PARAM_SYNTAX | Parameter syntax incorrect |
| 0x800CCC64 | SMTP_502_COMMAND_NOTIMPL | Command not implemented |
| 0x800CCC65 | SMTP_503_COMMAND_SEQ | Improper command sequence |
| 0x800CCC66 | SMTP_504_COMMAND_PARAM_NOTIMPL | Command not implemented |
| 0x800CCC67 | SMTP_421_NOT_AVAILABLE | Command not available |
| 0x800CCC68 | SMTP_450_MAILBOX_BUSY | Mailbox is locked and busy |
| 0x800CCC69 | SMTP_550_MAILBOX_NOT_FOUND | Mailbox not found |
| 0x800CCC6A | SMTP_451_ERROR_PROCESSING | Error processing request |
| 0x800CCC6B | SMTP_551_USER_NOT_LOCAL | User mailbox is known, but mailbox not on this server |
| 0x800CCC6C | SMTP_452_NO_SYSTEM_STORAGE | No space to store messages |
| 0x800CCC6D | SMTP_552_STORAGE_OVERFLOW | Storage limit exceeded |
| 0x800CCC6E | SMTP_553_MAILBOX_NAME_SYNTAX | Invalid mailbox name syntax |
| 0x800CCC6F | SMTP_554_TRANSACT_FAILED | Transaction failed |
| 0x800CCC78 | SMTP_REJECTED_SENDER | Unknown sender. This is caused by having the incorrect e-mail address in the Reply-To field |
| 0x800CCC79 | SMTP_REJECTED_RECIPIENTS | Server rejected recipients |
| 0x800CCC7A | SMTP_NO_SENDER | No sender address specified |
| 0x800CCC7B | SMTP_NO_RECIPIENTS | No recipients specified |
