> For the complete documentation index, see [llms.txt](https://kasplo.gitbook.io/kasplo-doc/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://kasplo.gitbook.io/kasplo-doc/channels/email-verification/status-guide.md).

# Status Guide

### Kasplo Email Verification Status Guide

This guide outlines how Kasplo classifies email addresses based on SMTP verification and what each status means in terms of email campaign safety. This can help developers and marketers make informed decisions when sending campaigns through the Kasplo platform or using our Email Verification API.

### Healthy Statuses (Recommended for Sending)

| Status     | Safe to Send | Description                                                                                                                                                    |
| ---------- | ------------ | -------------------------------------------------------------------------------------------------------------------------------------------------------------- |
| good       | Yes          | Mailbox is valid and accepted by the recipient server via SMTP handshake. Fully verified.                                                                      |
| unverified | Cautious     | Server doesn't allow mailbox verification (e.g., catch-all or VRFY disabled). Email may or may not exist. Safe to send to well-known domains (Gmail, Outlook). |

### Risky or Unsafe Statuses (Not Recommended for Sending)

| Status     | Safe to Send | Description                                                                                    |
| ---------- | ------------ | ---------------------------------------------------------------------------------------------- |
| bademail   | No           | Mailbox confirmed to not exist. Sending them will result in hard bounces.                      |
| bad        | No           | SMTP connection or flow failed (e.g., 554 policy rejection, 503 sequence error).               |
| unknown    | No           | Domain cannot be resolved or mail server is unreachable. Likely due to DNS or MX issues.       |
| timeout    | No (Retry)   | No response from server within allowed time. May be temporary; retry before marking as failed. |
| greylisted | No (Retry)   | The recipient server has temporarily deferred your attempt. Retry after a short delay.         |

### How Kasplo Determines Status

Kasplo performs a real-time SMTP verification using the following steps:

1. **DNS & MX Lookup**: Validates domain and mail server existence.
2. **SMTP Handshake**: Initiates connection with the mail server.
3. **MAIL FROM & RCPT TO Checks**: Determines if mailbox exists.
4. **Command Analysis**: Analyzes server responses using standard SMTP codes.
5. **Classification**: Assigns a status based on response and behavior.

### SMTP Response Mapping

| Code                    | Status               | Description                                    |
| ----------------------- | -------------------- | ---------------------------------------------- |
| 220, 250, 251           | good                 | Server accepted connection and mailbox         |
| 354, 421                | good                 | Server ready for data (positive step)          |
| 550, 551, 552, 553, 555 | bademail             | Mailbox rejected or doesn't exist              |
| 450, 451, 452, 455      | greylisted           | Temporary issues (rate limiting, greylisting)  |
| 503                     | bad                  | Bad sequence of commands                       |
| 502, 504, 530, 535, 538 | unverified           | Server doesn't support command or rejects auth |
| 454                     | unverified / timeout | TLS or readiness issue                         |
| 554, 521                | bad                  | Server refused connection or mail              |
| Timeout / No Response   | timeout              | No response from server                        |
| No MX / DNS Error       | unknown              | Domain/server unreachable                      |
| Invalid Email Syntax    | bademail             | Email format invalid                           |

### Kasplo Best Practice Recommendations

* Send to **good**: These are fully validated and safe.
* Optionally send to **unverified** : Especially for known domains like Gmail, but avoid excessive volume.
* Retry greylisted and timeout: Wait and re-check within 6–12 hours.
* Never send to bademail, bad, or unknown: Protects your sender reputation.

### Notes for Developers

* This classification is returned as part of our Email Verification API response.
* Use these statuses to segment, filter, or clean your email list automatically.
* You can configure Kasplo to automatically suppress unsafe addresses from future campaigns.

For any questions or integration help, reach out to <helpdesk@kasplo.com>.