> 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/admin-portal/settings/smtp-client.md).
# SMTP Client
How Sendman treats the clients, devices and applications that connect to it
The **SMTP Client Settings** page controls how Sendman treats the mail clients, devices and applications that connect to it.
## Legacy TLS cipher suites
Some older devices, such as printers or scanners, cannot establish a TLS connection with Sendman because they only support outdated cipher suites. Their TLS handshake fails, often with an error like *no shared cipher*.
When you switch on **Allow legacy TLS cipher suites**, Sendman additionally accepts the following cipher suites for **TLS 1.2**:
* `TLS_RSA_WITH_AES_256_GCM_SHA384`
* `TLS_RSA_WITH_AES_128_GCM_SHA256`
* `TLS_RSA_WITH_AES_256_CBC_SHA256`
* `TLS_RSA_WITH_AES_128_CBC_SHA256`
* `TLS_RSA_WITH_AES_256_CBC_SHA`
* `TLS_RSA_WITH_AES_128_CBC_SHA`
TLS 1.3 and the default cipher suites remain unchanged. The setting applies to new connections; no restart is needed.
{% hint style="warning" %}
These cipher suites use static RSA key exchange, which offers no forward secrecy, and CBC-SHA is outdated. The setting applies to all clients of your instance. Leave it off unless a device needs it, and check for firmware updates of the device first.
{% endhint %}
{% hint style="info" %}
Devices that only support TLS 1.0 or 1.1 cannot connect with TLS, even with this setting. Connect them through a [network connection](/admin-portal/settings/network-connections.md) and let them send on port 25 without TLS.
{% endhint %}
---
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