> ## 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.

# DMARC enforcement in MailChannels Inbound Filtering

> How MailChannels enforces DMARC policies on inbound mail and how the sender's DMARC policy interacts with your spam handling configuration.

DMARC (Domain-based Message Authentication, Reporting & Conformance) is an email authentication standard that lets domain owners publish a policy instructing receiving mail servers how to handle messages that fail SPF or DKIM alignment checks. When a sender's domain has a DMARC policy, MailChannels reads and enforces it on all inbound messages.

The action MailChannels takes depends on the combination of the sender's published DMARC policy and the spam handling policy you have configured for your protected domain.

| Sender DMARC policy | Your spam handling policy | MailChannels action |
| ------------------- | ------------------------- | ------------------- |
| `p=reject`          | block                     | block               |
| `p=reject`          | quarantine                | block               |
| `p=reject`          | flag                      | block               |
| `p=quarantine`      | block                     | block               |
| `p=quarantine`      | quarantine                | quarantine          |
| `p=quarantine`      | flag                      | flag                |
| `p=none`            | block                     | none                |
| `p=none`            | quarantine                | none                |
| `p=none`            | flag                      | none                |

When the sending domain publishes `p=reject`, MailChannels blocks unauthorized messages regardless of your local spam handling policy. When the sender uses `p=none`, DMARC monitoring mode applies and no DMARC-based action is taken.

Senders whose messages are rejected due to DMARC will receive a `550 5.7.1 Unauthenticated email is not accepted due to domain's DMARC policy` error. See [SMTP errors](/inbound/smtp-errors) for more detail.

To change how your domain handles spam, see [Configure spam handling](/inbound/domain-admins#configure-spam-handling).