cdc.gov

cdc.gov · Last checked 2026-10-04 02:08 UTC

cdc.gov

Needs work, with 2 things to fix

cdc.gov scored 62/100 (grade C). The main issues are no SPF record and DKIM key shorter than 2048 bits. Detected senders: Microsoft 365.

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

3 passed1 needs attention1 failing3 for informationDetected senders: Microsoft 365
Fix this firstThe change with the biggest effect

Publish an SPF record

Lists the sending services detected for cdc.gov (Microsoft 365) and rejects everything else. Add any other service that sends as cdc.gov before publishing. Changes: Added include:spf.protection.outlook.com for Microsoft 365.

TypeTXT
Name / Host
cdc.gov

Some DNS providers want “@” here instead of the full domain.

Value
v=spf1 include:spf.protection.outlook.com -all

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. Add a new TXT record with the name and value above.
  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?No SPF recordFailing
  • Fail: No SPF record

    cdc.gov publishes no TXT record starting with "v=spf1", so receivers cannot tell which servers may send mail for it. Publish one SPF record listing every service that sends as cdc.gov.

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

    k1 (1024-bit), s2 (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.

  • Pass: DKIM key published

    cdc.gov publishes a DKIM key under selector1, selector2, k1, s1, s2.

DMARCWhat happens to fakes?No issues foundPass

Nothing to report.

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.cdc.gov. 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.cdc.gov. 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.cdc.gov. 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 cdc.gov publishes an MTA-STS policy at https://mta-sts.cdc.gov/.well-known/mta-sts.txt. Change the id whenever the policy file changes.

TypeTXT
Name / Host
_mta-sts.cdc.gov

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.cdc.gov. 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.cdc.gov/.well-known/mta-sts.txt
Contents
version: STSv1
mode: testing
mx: primary.us.etp.fireeyegov.com
mx: alt1.us.etp.fireeyegov.com
mx: alt2.us.etp.fireeyegov.com
mx: alt3.us.etp.fireeyegov.com
max_age: 604800

Set up a TLS report addressinstruction

Sending servers will report TLS failures when delivering to cdc.gov, 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.cdc.gov

  1. Pick an address that will receive TLS reports: a mailbox you read (for example tls-reports@cdc.gov, created first) or a TLS reporting service. 2. Publish a TXT record at _smtp._tls.cdc.gov 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.cdc.gov

  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://cdc.gov/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.cdc.gov with v=BIMI1, l= set to the logo URL and a= set to the certificate URL.