DMARC vs DMARCbis Checker

This tool validates your domain's DMARC record against both the original DMARC standard (RFC 7489) and the updated DMARCbis specification (RFC 9091). It checks record syntax, reports issues such as duplicate records or invalid tags, and shows how your effective policy resolves under each protocol side by side.

Enter any domain or subdomain above and click Check DMARC to see the full domain hierarchy, every DNS level queried, the effective policy at each level, and any errors or warnings in your records.

DMARCbis is the updated DMARC specification defined in RFC 9091 that replaces the original RFC 7489. The key change is how receiving mail servers discover DMARC policies for subdomains.

Under original DMARC, policy discovery only checks two DNS locations: the exact domain and the organizational domain. DMARCbis introduces the tree walk algorithm that checks every intermediate domain level. For example, news.marketing.example.bank under DMARCbis queries:

1. _dmarc.news.marketing.example.bank
2. _dmarc.marketing.example.bank
3. _dmarc.example.bank
4. _dmarc.bank

The first record found becomes the effective policy. This means a DMARC record at an intermediate level like _dmarc.marketing.example.bank is used by DMARCbis but ignored by original DMARC, which would skip straight to the organizational domain. This can produce different effective policies depending on which protocol the receiver uses.

In most cases, existing DMARC records continue to work under DMARCbis. However, if you use subdomains, run a DMARCbis check to verify that both protocols resolve your policies as expected before mail receivers start adopting DMARCbis.

Organizations with complex subdomain structures may benefit from publishing DMARC records at intermediate levels to take advantage of the granular policy control DMARCbis provides.

Yes. Major German inbox providers, including GMX, mail.com, and WEB.DE, are already running DMARCbis in production and sending DMARC aggregate reports that follow the updated specification. Other providers are expected to follow as DMARCbis adoption grows.

This means the tree walk algorithm is no longer theoretical. It is actively being used to resolve DMARC policies for incoming mail. If your domain relies on subdomains, checking your records against both standards now helps you prepare for how your policy will actually be evaluated.