> ## Documentation Index
> Fetch the complete documentation index at: https://docs.mailchannels.com/llms.txt
> Use this file to discover all available pages before exploring further.

# Internationalized domain names (IDNs) in Inbound Filtering

> Protect internationalized domain names (IDNs) with MailChannels Inbound Filtering, including Punycode-encoded domains and non-ASCII top-level domains.

An internationalized domain name (IDN) is a domain name that contains non-ASCII characters ? Arabic, Chinese, Cyrillic, accented Latin letters, and so on. Because DNS only supports ASCII characters, IDNs are encoded using [Punycode](https://datatracker.ietf.org/doc/html/rfc5891), which converts Unicode characters into an ASCII-compatible form. Punycode-encoded domain labels begin with the prefix `xn--`.

For example:

| Unicode (U-label) | Punycode (A-label)      |
| ----------------- | ----------------------- |
| `m?nchen.de`      | `xn--mnchen-3ya.de`     |
| `??.jp`           | `xn--r8jz45g.jp`        |
| `?????.??`        | `xn--80a1acny.xn--p1ai` |

MailChannels Inbound Filtering supports both second-level IDNs and internationalized top-level domains (TLDs).

## How MailChannels handles IDNs

When you add an IDN, MailChannels automatically registers both its Unicode (U-label) form and its Punycode (A-label) equivalent. This ensures mail is filtered correctly regardless of which form a sending server presents.

Email authentication checks (including SPF) convert U-labels to A-labels before performing DNS lookups, so records published under Punycode domain names are evaluated correctly. MX record verification in the Domain Console applies the same conversion.

## Add an IDN

Add an IDN the same way you add any domain ? single entry or CSV bulk upload in the Host Console, or via the Provisioning API. See [domain management](/inbound/domains) for the full steps.

You can enter the domain in either its Unicode form (`m?nchen.de`) or its Punycode form (`xn--mnchen-3ya.de`). MailChannels handles both.

<Note>
  If you use the cPanel/WHM plugin to provision domains, IDN domains are supported and can be added directly through the plugin.
</Note>

## IDNs and domain aliases

If you add an IDN as a [domain alias](/inbound/domain-alias), MailChannels automatically creates a second alias for the Punycode equivalent. Deleting the Unicode alias also removes the Punycode alias. You do not need to manage both manually.

## Convert between Unicode and Punycode

Use a tool like [punycoder.com](https://www.punycoder.com/) to convert between the Unicode and Punycode forms of a domain.