github.com
Good, with 5 things to fix
github.com scored 84/100 (grade B). The main issues are DKIM key shorter than 2048 bits and SPF is close to the 10-lookup limit, plus 4 more. Detected senders: Google Workspace, Microsoft 365, SendGrid, Mailchimp, Zendesk and Salesforce.
Checked 2026-10-02 12:29 UTC · fresh check
Diagnosis notes
- Warning: DNS lookup budget exhausted
This diagnosis stopped sending DNS queries after 8000 ms. Checks that needed more lookups report their remaining results as unknown; the domain's records may be unusually large or slow to answer.
Reduce SPF DNS lookups
Evaluating SPF for github.com takes 10 DNS lookups including nested includes; receivers stop at 10 and fail SPF. No detected sending service accounts for these includes; remove each one you no longer send through: _netblocks.google.com, _netblocks2.google.com, mktomail.com. Changes: Added include:_spf.google.com for Google Workspace. Replaced ~all with -all so mail from servers not listed is rejected.
github.com
Some DNS providers want “@” here instead of the full domain.
v=spf1 ip4:192.30.252.0/22 include:spf.protection.outlook.com include:_netblocks.google.com include:_netblocks2.google.com include:mail.zendesk.com include:_spf.salesforce.com include:servers.mcsv.net include:mktomail.com include:sendgrid.net ip4:62.253.227.114 ip4:166.78.69.169 ip4:166.78.69.170 ip4:166.78.71.131 include:_spf.google.com -all
v=spf1 ip4:192.30.252.0/22 include:spf.protection.outlook.com include:_netblocks.google.com include:_netblocks2.google.com include:mail.zendesk.com include:_spf.salesforce.com include:servers.mcsv.net include:mktomail.com include:sendgrid.net ip4:62.253.227.114 ip4:166.78.69.169 ip4:166.78.69.170 ip4:166.78.71.131 ~all
How to apply it
- Sign in where your domain’s DNS is managed. This is often where you bought the domain, such as Cloudflare, GoDaddy or Namecheap.
- Find the existing TXT record with that name and replace its value.
- 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?Could not look up MX recordsNeeds attention
- Warning: Could not look up MX records
Some DNS queries needed to check mail delivery for github.com failed (A github-com.mail.protection.outlook.com: TIMEOUT; AAAA github-com.mail.protection.outlook.com: TIMEOUT), so the result is unknown. Try again later; if it persists, check the nameservers involved.
- Info: Only one MX host
All mail for github.com goes to github-com.mail.protection.outlook.com. Most hosted providers make that one name highly available; if you run your own server, consider a backup MX.
SPFWho may send as you?SPF is close to the 10-lookup limitNeeds attention
- Warning: SPF is close to the 10-lookup limit
Evaluating the SPF record for github.com needs 10 of the 10 allowed DNS lookups. Adding one more service, or a provider growing its own record, will break SPF.
How to fix this - Info: SPF ends in softfail (~all)
"~all" is common and works well with DMARC. "-all" is stricter; switch when you are sure every sender is listed.
DKIMAre your emails signed?DKIM key shorter than 2048 bitsNeeds attention
- Warning: DKIM key shorter than 2048 bits
selector1 (1024-bit), k1 (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
github.com publishes a DKIM key under google, selector1, k1, k2, k3, s1, s2.
DMARCWhat happens to fakes?DMARC policy is quarantine; consider rejectInfo
- Info: DMARC policy is quarantine; consider reject
Failing mail goes to spam rather than being refused. When reports show no legitimate failures, reject gives the strongest protection.
How to fix this
AlignmentDoes it match your From?No issues foundPass
Nothing to report.
BIMICan inboxes show your logo?Could not look up the BIMI recordNeeds attention
- Warning: Could not look up the BIMI record
The TXT query for default._bimi.github.com returned TIMEOUT, so BIMI status is unknown. Try again later.
MTA-STSIs mail to you encrypted?Could not look up the MTA-STS recordNeeds attention
- Warning: Could not look up the MTA-STS record
The TXT query for _mta-sts.github.com returned TIMEOUT, so MTA-STS status is unknown. Try again later.
TLS-RPTWill you hear about failures?No TLS-RPT recordInfo
- Info: No TLS-RPT record
No TLS reporting record at _smtp._tls.github.com. TLS-RPT (RFC 8460) tells senders where to send daily reports about failed encrypted deliveries to you.
How to fix this
Other fixes
Strengthen the DMARC policyTXT
Rejects mail that fails DMARC, the strongest protection against spoofing.
_dmarc.github.com
Some DNS providers want just “_dmarc” here.
v=DMARC1; p=reject; rua=mailto:dmarc@github.com; adkim=r; aspf=r
v=DMARC1; p=quarantine; sp=reject; pct=100; rua=mailto:dmarc@github.com; ruf=mailto:dmarc@github.com; fo=1
Set up a TLS report addressinstruction
Sending servers will report TLS failures when delivering to github.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.github.com
- Pick an address that will receive TLS reports: a mailbox you read (for example tls-reports@github.com, created first) or a TLS reporting service. 2. Publish a TXT record at _smtp._tls.github.com with the value v=TLSRPTv1; rua=mailto:<that address>.