opendns.com

opendns.com · Last checked 2026-10-04 02:08 UTC

opendns.com

Needs work, with 3 things to fix

opendns.com scored 61/100 (grade C). The main issues are DMARC policy is none and DKIM key shorter than 2048 bits, plus 2 more. Detected senders: Google Workspace, Amazon SES and Zendesk.

Checked 2026-10-04 02:08 UTC · fresh check

2 passed3 need attention0 failing3 for informationDetected senders: Google Workspace, Amazon SES, Zendesk
Fix this firstThe change with the biggest effect

Strengthen the DMARC policy

Quarantines 25% of mail that fails DMARC, a safe first step: check the reports for legitimate senders that fail before going further.

TypeTXT
Name / Host
_dmarc.opendns.com

Some DNS providers want just “_dmarc” here.

Value
v=DMARC1; p=quarantine; pct=25; rua=mailto:hostmaster@opendns.com; adkim=r; aspf=r
Replaces
v=DMARC1; p=none; rua=mailto:hostmaster@opendns.com

How to apply it

  1. Sign in where your domain’s DNS is managed. This is often where you bought the domain, such as Cloudflare, GoDaddy or Namecheap.
  2. Find the existing TXT record with that name and replace its value.
  3. Save, then come back and re-check. DNS changes can take up to a few hours to show.

All checks

MXCan servers find your inbox?No issues foundPass

Nothing to report.

SPFWho may send as you?SPF uses the ptr mechanismNeeds attention
  • Warning: SPF uses the ptr mechanism

    The SPF record of opendns.com uses ptr. RFC 7208 §5.5 says ptr "SHOULD NOT be used": it is slow, unreliable, and some receivers ignore it. Replace it with ip4/ip6 ranges or an include from your provider.

  • Warning: SPF ends in neutral (?all)

    "?all" tells receivers to treat mail from unlisted servers as neither pass nor fail, so SPF gives no protection. End the record with "-all" or "~all".

DKIMAre your emails signed?DKIM key shorter than 2048 bitsNeeds attention
  • Warning: DKIM key shorter than 2048 bits

    google (1024-bit), mail (1024-bit), default (1024-bit) uses an RSA key below 2048 bits. Short keys can be factored and some receivers treat them as weak. Rotate to a 2048-bit key at your sending provider.

  • Info: DKIM key is in testing mode

    mail, default sets t=y, which asks receivers to treat DKIM results as a test. Remove t=y once signing works so failures count.

  • Pass: DKIM key published

    opendns.com publishes a DKIM key under google, mail, default.

DMARCWhat happens to fakes?DMARC policy is noneNeeds attention
  • Warning: DMARC policy is none

    A none policy only monitors: mail that fails DMARC is still delivered, so anyone can spoof the domain. Once reports show your legitimate senders pass, move to quarantine and then reject.

    How to fix this
AlignmentDoes it match your From?No issues foundPass

Nothing to report.

BIMICan inboxes show your logo?No BIMI recordInfo
  • Info: No BIMI record

    No BIMI record at default._bimi.opendns.com. BIMI is optional: it shows your logo next to your mail in supporting inboxes once DMARC is enforced.

    How to fix this
MTA-STSIs mail to you encrypted?No MTA-STS recordInfo
  • Info: No MTA-STS record

    No MTA-STS record at _mta-sts.opendns.com. MTA-STS (RFC 8461) makes sending servers require TLS and a valid certificate when delivering to you, which blocks downgrade attacks.

    How to fix this
TLS-RPTWill you hear about failures?No TLS-RPT recordInfo
  • Info: No TLS-RPT record

    No TLS reporting record at _smtp._tls.opendns.com. TLS-RPT (RFC 8460) tells senders where to send daily reports about failed encrypted deliveries to you.

    How to fix this

Other fixes

Publish the MTA-STS recordTXT

Tells sending servers that opendns.com publishes an MTA-STS policy at https://mta-sts.opendns.com/.well-known/mta-sts.txt. Change the id whenever the policy file changes.

TypeTXT
Name / Host
_mta-sts.opendns.com

Some DNS providers want just “_mta-sts” here.

Value
v=STSv1; id=202610040208

Host the MTA-STS policy filepolicy-file

Serve this file over HTTPS with a valid certificate for mta-sts.opendns.com. It lists your MX hosts and starts in testing mode; switch to mode: enforce once TLS-RPT reports show no failures.

Location
https://mta-sts.opendns.com/.well-known/mta-sts.txt
Contents
version: STSv1
mode: testing
mx: alln-mx-01.cisco.com
mx: rcdn-mx-01.cisco.com
mx: aer-mx-01.cisco.com
max_age: 604800

Set up a TLS report addressinstruction

Sending servers will report TLS failures when delivering to opendns.com, which you need before enforcing MTA-STS. The address must accept TLS reports; a DMARC report address does not necessarily do so.

Applies to: _smtp._tls.opendns.com

  1. Pick an address that will receive TLS reports: a mailbox you read (for example tls-reports@opendns.com, created first) or a TLS reporting service. 2. Publish a TXT record at _smtp._tls.opendns.com with the value v=TLSRPTv1; rua=mailto:<that address>.

Prepare BIMIinstruction

BIMI shows your logo next to messages in supporting inboxes, but only for mail that passes DMARC under an enforced policy.

Applies to: default._bimi.opendns.com

  1. Enforce DMARC first: p=quarantine or p=reject at 100% (no pct below 100). 2. Convert your logo to an SVG Tiny PS file and host it over HTTPS, for example https://opendns.com/bimi/logo.svg. 3. For Gmail and Apple Mail, obtain a VMC or CMC certificate for the logo. 4. Publish a TXT record at default._bimi.opendns.com with v=BIMI1, l= set to the logo URL and a= set to the certificate URL.