zendesk.com
The three core checks pass. What is missing is the transport and trust layer around them.
4 of 8 checks pass · 6 tools visible in DNS · nothing urgent
1 · Authentication and transport
SPF
PassValid, soft failAnything not on the list is accepted but marked. Google recommends ~all; with DMARC enforced it is as strong as -all.
v=spf1 ip4:103.151.192.0/23 ip4:104.43.243.237 ip4:149.97.173.180 ip4:163.116.128.0/17 ip4:170.10.128.0/24 ip4:170.10.129.0/24 ip4:170.10.132.56/29 ip4:170.10.132.64/29 ip4:170.10.133.0/24 ip4:18.194.95.56 ip4:18.198.96.88 include:_spf1.zendesk.com ~all
DKIM
Pass8 keys foundSelectors k1, k2, k3, s1, s2, mandrill, hs1, hs2 publish a public key. 7 of them point at a vendor by CNAME.
k1._domainkey, k2._domainkey, k3._domainkey, s1._domainkey, s2._domainkey, mandrill._domainkey, hs1._domainkey, hs2._domainkey
DMARC
PassEnforced (p=reject)Failing mail is rejected. This is the finish line.
v=DMARC1; p=reject
- No "rua=" address — you will not receive aggregate reports.
- No rua= address, so nobody receives the aggregate reports.
MX
Pass6 hostsMore than one receiving server, so a single outage does not bounce mail.
10 us-smtp-inbound-1.mimecast.com 20 us-smtp-inbound-2.mimecast.com 30 aspmx.l.google.com 40 alt1.aspmx.l.google.com 50 alt2.aspmx.l.google.com 60 aspmx2.googlemail.com
MTA-STS
ReviewNot publishedSending servers cannot tell that this domain requires TLS, so inbound mail can be downgraded to plain text by anyone on the path.
TLS-RPT
OptionalNot publishedNobody is told when TLS to this domain fails. Cheap to add once MTA-STS is in place.
BIMI
OptionalNot publishedDMARC is enforced, so this domain qualifies. Yahoo and Fastmail show the logo from the record alone; Gmail and Apple Mail also need a paid VMC or CMC certificate.
DNSSEC
OptionalNot signedOptional. Signing the zone protects every record in this report from tampering.
2 · Tools visible in DNS
| Layer | Tool | Evidence |
|---|---|---|
| Mailbox | Google Workspace | MX aspmx.l.google.com |
| Gateway | Mimecast | MX us-smtp-inbound-1.mimecast.com |
| Marketing | Mailchimp | DKIM k1._domainkey → dkim.mcsv.net |
| Marketing | HubSpot | DKIM hs1._domainkey → zendesk-com.hs01a.dkim.hubspotemail.net |
| Transactional | SendGrid | DKIM s1._domainkey → s1.domainkey.u18413.wl164.sendgrid.net |
| Support | Zendesk | SPF include:_spf1.zendesk.com |
Only tools that leave a DNS trace appear. A shared DKIM selector is attributed only when its CNAME target names the vendor.
3 · Sender requirements (Google, Yahoo, Microsoft)
| Requirement | Applies to | Status | Note |
|---|---|---|---|
| Authenticate with SPF or DKIM | GoogleYahooMicrosoft | Verified | At least one method is in place. |
| Bulk senders: both SPF and DKIM | GoogleYahoo | Verified | Both are present. |
| Publish a DMARC record (p=none is enough) | GoogleYahooMicrosoft | Verified | Policy is p=reject. |
| From: domain aligns with SPF or DKIM | GoogleYahooMicrosoft | Not checkable here | Needs a real message. The Send-a-Test report will check this. |
| Valid forward and reverse DNS for sending IPs | GoogleYahoo | Not checkable here | Depends on the sending server, not the domain. |
| Encrypt in transit (TLS) | GoogleYahoo | Not checkable here | Outbound TLS depends on your sending tool; MTA-STS would cover inbound. |
| One-click unsubscribe (RFC 8058) for marketing mail | GoogleYahoo | Not checkable here | A message header, not a DNS record. Microsoft recommends it rather than requiring it. |
| Spam complaint rate under 0.1% (0.3% is the hard limit) | GoogleYahoo | Not checkable here | Read it in Google Postmaster Tools and Yahoo Sender Hub. Google’s target is 0.1%; 0.3% is where enforcement starts. |
4 · What to fix, in order
-
P2
Add a rua= address to DMARC
Without reports you cannot see who is failing, or who is spoofing you.
Publish at_dmarc.zendesk.comv=DMARC1; p=reject; rua=mailto:dmarc@zendesk.com
-
P3
Publish MTA-STS (record and policy file)
Tells sending servers to require TLS to your MX hosts, which prevents downgrade attacks. The TXT record alone does nothing: the policy file must be served over HTTPS at mta-sts.zendesk.com. Start in testing mode, watch TLS-RPT, then switch to enforce.
Publish at_mta-sts.zendesk.com and https://mta-sts.zendesk.com/.well-known/mta-sts.txtTXT v=STSv1; id=2026100401 mta-sts.txt: version: STSv1 mode: testing mx: us-smtp-inbound-1.mimecast.com mx: us-smtp-inbound-2.mimecast.com mx: aspmx.l.google.com mx: alt1.aspmx.l.google.com mx: alt2.aspmx.l.google.com mx: aspmx2.googlemail.com max_age: 86400
-
P3
Publish TLS-RPT
You get a report when TLS delivery to your domain fails; this is what notices a downgrade that MTA-STS is meant to prevent. The address must exist.
Publish at_smtp._tls.zendesk.comv=TLSRPTv1; rua=mailto:tls-rpt@zendesk.com
-
P3
Add a BIMI logo record (optional)
DMARC already qualifies. The logo must be SVG Tiny PS, square, served over HTTPS. Yahoo and Fastmail show it from the record alone; Gmail and Apple Mail also need a paid VMC or CMC certificate, and a VMC needs a registered trademark. Skip this unless the certificate is worth it to you.
Publish atdefault._bimi.zendesk.comv=BIMI1; l=https://zendesk.com/.well-known/bimi.svg;
-
P3
Sign the zone with DNSSEC
Protects every record in this report from being swapped in transit. Two steps: enable signing at your DNS host (one switch at Cloudflare and most others), then add the DS record it gives you at your registrar.
Publish atzendesk.com
Appendix · Raw DNS answers
| Name | Type | Answer |
|---|---|---|
| zendesk.com | MX | 10 us-smtp-inbound-1.mimecast.com 20 us-smtp-inbound-2.mimecast.com 30 aspmx.l.google.com 40 alt1.aspmx.l.google.com 50 alt2.aspmx.l.google.com 60 aspmx2.googlemail.com |
| zendesk.com | A | 216.198.54.2 216.198.53.2 |
| zendesk.com | TXT | v=spf1 ip4:103.151.192.0/23 ip4:104.43.243.237 ip4:149.97.173.180 ip4:163.116.128.0/17 ip4:170.10.128.0/24 ip4:170.10.129.0/24 ip4:170.10.132.56/29 ip4:170.10.132.64/29 ip4:170.10.133.0/24 ip4:18.194.95.56 ip4:18.198.96.88 include:_spf1.zendesk.com ~all (+ 45 other TXT records: site-verification tokens and the like, omitted) |
| _dmarc.zendesk.com | TXT | v=DMARC1; p=reject |
| <selector>._domainkey.zendesk.com | TXT | k1 → CNAME dkim.mcsv.net k2 → CNAME dkim2.mcsv.net k3 → CNAME dkim3.mcsv.net s1 → CNAME s1.domainkey.u18413.wl164.sendgrid.net s2 → CNAME s2.domainkey.u18413.wl164.sendgrid.net mandrill → key published hs1 → CNAME zendesk-com.hs01a.dkim.hubspotemail.net hs2 → CNAME zendesk-com.hs01b.dkim.hubspotemail.net |
| _mta-sts.zendesk.com | TXT | v=spf1 include:_netblocks.zdsys.com ~all |
| _smtp._tls.zendesk.com | TXT | v=spf1 include:_netblocks.zdsys.com ~all |
| default._bimi.zendesk.com | TXT | v=spf1 include:_netblocks.zdsys.com ~all |