Руководство Пользователя для Cisco Cisco Email Security Appliance C170

Domain-based Message Authentication, Reporting and Conformance (DMARC) is a technical 
specification created to reduce the potential for email-based abuse. DMARC standardizes how email 
receivers perform email authentication using SPF and DKIM mechanisms. To pass DMARC verification, 
an email must pass at least one of these authentication mechanisms, and the Authentication Identifiers 
must comply with RFC 5322.

AsyncOS for Email allows you to:

Verify incoming emails using DMARC.

Define profiles to override (accept, quarantine, or reject) domain owners’ policies.

Send feedback reports to domain owners, which helps to strengthen their authentication 
deployments.

Send delivery error reports to the domain owners if the DMARC aggregate report size exceeds 10 
MB or the size specified in the RUA tag of the DMARC record.

AsyncOS for Email can handle emails that are compliant with the DMARC specification as submitted 
to Internet Engineering Task Force (IETF) on March 31, 2013. For more information, see 

The following describes how AsyncOS for Email performs DMARC verification.

A listener configured on AsyncOS receives an SMTP connection.

AsyncOS performs SPF and DKIM verification on the message.

AsyncOS fetches the DMARC record for the sender’s domain from the DNS. 

If no record is found, AsyncOS skips the DMARC verification and continues processing. 

If the DNS lookup fails, AsyncOS takes action based on the specified DMARC verification 
profile.

Depending on DKIM and SPF verification results, AsyncOS performs DMARC verification on the 
message.

If DKIM and SPF verification is enabled, DMARC verification reuses the DKIM and SPF 
verification results.

Depending on the DMARC verification result and the specified DMARC verification profile, 
AsyncOS accepts, quarantines, or rejects the message. If the message is not rejected due to DMARC 
verification failure, AsyncOS continues processing.

AsyncOS sends an appropriate SMTP response and continues processing.

If sending of aggregate reports is enabled, AsyncOS gathers DMARC verification data and includes 
it in the daily report sent to the domain owners. For more information about the DMARC aggregate 
feedback report, see 

If the aggregate report size exceeds 10 MB or the size specified in the RUA tag of the 
DMARC record, AsyncOS sends delivery error reports to the domain owners.