# Limits & errors

What an IMAP mailbox can and cannot do through Zernio, its sending limit and health states, and the errors its connect and email calls return.

## Health

`GET /v1/accounts/{accountId}/health` returns `health.imap` and `health.smtp`, each with `status`, `lastSuccessAt` and `lastError`.

| Status | Meaning |
|--------|---------|
| `active` | The last poll succeeded |
| `degraded` | Network or certificate errors for under 30 minutes; polling retries |
| `reconnect_required` | The password stopped working; polling has stopped |

## What you cannot do

- Calendar, files and contacts: an IMAP connection is email only. Connect a Google or Microsoft account for those.
- Labels: IMAP has folders only. Move mail with `folder`.
- Gmail and Microsoft mail over IMAP: they connect with OAuth. Gmail app passwords work only through the hosted page's fallback for blocked Google sign-in.
- Proton Mail: it offers IMAP only through Proton Mail Bridge on the user's computer.
- Sending more than 200 emails a day from one mailbox.

## Common errors

| Code | Cause | Fix |
|------|-------|-----|
| `app_password_required` | The provider needs an app password | Create one at `details.helpUrl` |
| `imap_auth_failed` | The IMAP login was rejected | Check the password and IMAP access |
| `smtp_auth_failed` | The SMTP login was rejected | Pass separate SMTP credentials |
| `imap_disabled` | IMAP access is off | Turn it on at the provider |
| `imap_unreachable` | The IMAP server did not answer | Check the host and port |
| `smtp_unreachable` | The SMTP server did not answer | Try port 587 with STARTTLS |
| `tls_hostname_mismatch` | The certificate is for another name | Use the name in `details.suggestion` |
| `tls_untrusted` | The certificate cannot be verified | Ask the provider to fix it |
| `discovery_failed` | No settings were found | Pass `imap` and `smtp` yourself |
| `account_reconnect_required` | The account needs reconnecting | Use `details.reconnectUrl` |

## Related

- [Connect](/platforms/imap/connect)
- [Email](/platforms/imap/email)