> For the complete documentation index, see [llms.txt](https://docs.sendman.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.sendman.com/other/troubleshooting.md).

# Troubleshooting

## First steps

When a message does not arrive, work through these questions:

1. **Does the client reach Sendman at all?** If the connection is closed immediately without any reply, the client's address is not on the [IP Allow List](/admin-portal/sendman/ip-allow-list.md). Check which public address your client really uses, e.g. the address of your firewall.
2. **Does the TLS handshake succeed?** Check [Logs](/admin-portal/insights/logs.md) for a failed TLS handshake. Old devices may need [legacy TLS cipher suites](/admin-portal/settings/smtp-client.md).
3. **Does the sign-in succeed?** See `535` and `538` in [SMTP Reply Codes](/other/troubleshooting/smtp-reply-codes.md).
4. **Are sender and recipients allowed?** See `550` in [SMTP Reply Codes](/other/troubleshooting/smtp-reply-codes.md) and check the [authorization policies](/admin-portal/sendman/authorization-policies.md) that apply to the client.
5. **Does the backend accept the message?** Replies of your [SMTP backend](/admin-portal/settings/smtp-backend.md) are passed on to the client unchanged and appear in the logs.

{% content-ref url="/pages/U3qHCZUdaA4S1m0FzSfe" %}
[SMTP Reply Codes](/other/troubleshooting/smtp-reply-codes.md)
{% endcontent-ref %}

## Common problems

### The connection is closed without a reply

The client's source address is not on the [IP Allow List](/admin-portal/sendman/ip-allow-list.md). Remember:

* Over the internet, Sendman sees the public address of your internet connection, not the client's local address.
* Over a [network connection](/admin-portal/settings/network-connections.md), Sendman sees the client's local address.
* Only IPv4 addresses are supported.

### The client signs in, but every message is rejected

No [authorization policy](/admin-portal/sendman/authorization-policies.md) applies to the client, or the policy that applies does not allow the sender address. Remember:

* A credential only takes effect once a policy references its username.
* Usernames in policies are compared exactly, including upper and lower case.
* Only the applicable policies with the lowest priority value are used. A more specific policy with a lower value can override a broader one.

### Entra ID sign-in fails although the password is correct

Sendman validates Entra ID passwords directly with Microsoft Entra ID. The sign-in fails if multi-factor authentication or a Conditional Access policy requires more than the password, or if the client uses AUTH NTLM. Use a dedicated service account without MFA for the device, or a [Sendman credential](/admin-portal/sendman/smtp-credentials.md).

### A printer or scanner reports a TLS or SSL error

The device probably only offers outdated cipher suites. See [Printers & Scanners](/configuration/get-started/scenario-based-guides/printers-and-scanners.md#tls-handshake-fails).

### Large scans are rejected

Messages are limited to 25 MB, or to the lower limit of your SMTP backend. Attachments grow by about one third during sending. Reduce the scan resolution or split the scan.


---

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