> ## 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.

# Configure your mail server for MailChannels Outbound Filtering

> Configure your MTA to relay outbound mail through MailChannels as a smart host, with connection details, SASL authentication, TLS, and sender identification headers.

To use MailChannels Outbound Filtering, you configure your mail transfer agent (MTA) to use MailChannels as a smart host—also called an SMTP relay. Instead of delivering email directly to recipients, your mail server hands every outbound message to MailChannels, which filters it, manages IP reputation, and delivers it on your behalf.

## Before you begin

You need:

* A MailChannels Outbound Filtering account
* Your SMTP username (same as "Account ID" in the Host Console under **Settings > Account > SMTP Passwords**)
* An SMTP password (create one in the Host Console if you haven't already)
* Access to your mail server's configuration

<Tip>
  TLS encryption is required for all connections from your mail server to MailChannels. Do not configure your MTA to use legacy SSL-mode encryption.
</Tip>

## Connection details

Use these settings when configuring your MTA:

| Setting        | Value                                                  |
| -------------- | ------------------------------------------------------ |
| Relay host     | `smtp.mailchannels.net`                                |
| Port           | `25` (preferred), `587` (STARTTLS), or `2525`          |
| Encryption     | TLS (STARTTLS)                                         |
| Authentication | SMTP AUTH with your MailChannels username and password |

If port 25 is blocked in your network or by your hosting provider, use port **587** with STARTTLS or port **2525** as a fallback.

## Set up your mail server

<Steps>
  <Step title="Get your credentials">
    Log in to the [Host Console](https://console.mailchannels.net) and go to **Settings > Account > SMTP Passwords**. Your SMTP username (Account ID) is shown on this page. If you don't have a password yet, create one here.
  </Step>

  <Step title="Configure the smart host">
    In your MTA configuration, set the relay or smart host to `smtp.mailchannels.net`. The exact setting name varies by MTA — refer to the guide for your specific mail server below.
  </Step>

  <Step title="Enable SMTP authentication">
    Configure your MTA to authenticate to `smtp.mailchannels.net` using the username and password from the Host Console. Use PLAIN or LOGIN SASL mechanisms over a TLS-encrypted connection.
  </Step>

  <Step title="Enable TLS">
    Set your MTA to require TLS when connecting to the MailChannels relay. Connections without TLS are rejected.
  </Step>

  <Step title="Set up SPF records">
    Update your domain's SPF records to authorize MailChannels to send on your behalf. Without this step, receiving mail servers may reject your messages. See [Set up SPF records](/outbound/spf-records) for instructions.
  </Step>

  <Step title="Set up monitors">
    After your mail server is relaying through MailChannels, configure monitors in the Host Console so you're notified when a compromised sender is detected. See [Monitors and alerts](/outbound/monitors-alerts).
  </Step>
</Steps>

<Note>
  Monitors are only available in Standard Plans and above
</Note>

## Sender identification headers

To help MailChannels track individual senders accurately, your MTA should add identification headers to each message. These headers let the system attribute email to a specific user, application, or script — which is essential for isolating compromised accounts without blocking everyone else.

<Tip>
  Add **X-AuthUser** header

  This X-AuthUser header often contains the authenticated sender address but can contain any unique identifier which you can use to locate the responsible sending entity.
</Tip>

The MTA-specific configuration guides contain details on how to insert the X-AuthUser header.

## MTA-specific setup guides

Choose the guide that matches your mail server:

<CardGroup cols={2}>
  <Card title="Postfix" href="/outbound/mta/setup-postfix">
    Configure Postfix relayhost and SASL authentication for MailChannels.
  </Card>

  <Card title="cPanel / Exim" href="/outbound/mta/setup-cpanel">
    Set up MailChannels as the smart host in WHM and cPanel environments.
  </Card>

  <Card title="Exim (advanced)" href="/outbound/mta/setup-exim">
    Advanced Exim configuration for custom routing and per-domain relay settings.
  </Card>

  <Card title="Microsoft Exchange" href="/outbound/mta/setup-exchange">
    Configure Exchange 2019 to send outbound mail through MailChannels.
  </Card>

  <Card title="Sendmail" href="/outbound/mta/setting-up-for-sendmail">
    Configure Sendmail with SASL authentication and smart host routing.
  </Card>

  <Card title="Zimbra" href="/outbound/mta/setup-zimbra">
    Route outbound mail through MailChannels and add X-AuthUser headers in Zimbra.
  </Card>

  <Card title="DirectAdmin" href="/outbound/mta/setting-up-for-directadmin">
    Configure Exim on DirectAdmin servers to relay through MailChannels.
  </Card>

  <Card title="SmarterMail" href="/outbound/mta/setting-up-for-smartermail">
    Set up an outgoing gateway and authenticated sender headers in SmarterMail.
  </Card>
</CardGroup>

For a full list of supported mail servers, see the **MTA Setup** section in the sidebar. If your MTA is not listed, look for "smart host" or "relay host" configuration options in your mail server's documentation, or contact [MailChannels support](mailto:support@mailchannels.com) for guidance.