Mail domain report: duo.nl

SPF

pass

SPF record published

Found

Record: v=spf1 mx a ip4:62.112.225.180 ip4:89.221.178.154 ip4:212.159.201.77 ip4:212.159.201.78 include:spf.protection.outlook.com ~all
DNS lookups: 3 of 10
Void lookups: 0 of 2

Checks

✓ No deprecated ptr mechanism #1

No ptr mechanism found in SPF record.
✓ 3 of 10 DNS lookups #2

SPF record needs 3 DNS lookups (limit is 10).
✓ Ends with ~all #3

SPF record properly uses ~all to restrict unauthorized senders.
✓ Record published #6

SPF record exists for this domain.
✓ Single record #16

Exactly one SPF record is published.
✓ Valid syntax #25

All SPF mechanisms and modifiers are valid.
✓ No void lookups #26

All include/redirect targets exist.
✓ No overly broad IP ranges #27

All ip4/ip6 ranges are narrow enough.

DMARC

warn

p=quarantine (_dmarc.duo.nl)

Found

Record: v=DMARC1;p=quarantine;rua=mailto:rua@duo.nl;adkim=r;aspf=r;pct=100;sp=reject
Found at: _dmarc.duo.nl

Tag	Value	Meaning
v	DMARC1	Version
p	quarantine	Policy
sp	reject	Subdomain policy
pct	100	Percentage of mail the policy applies to
rua	mailto:rua@duo.nl	Aggregate report addresses
adkim	r	DKIM alignment (r = relaxed, s = strict)
aspf	r	SPF alignment (r = relaxed, s = strict)

Checks

!

Policy: quarantine

DMARC policy is set to 'quarantine'. Consider upgrading to 'reject' for stronger protection once you've verified legitimate emails are passing authentication.

#4
✓ Record published #5

DMARC record exists for this domain.
✓ Valid syntax #17

DMARC record syntax is valid.
✓ Applies to 100% of mail #18

DMARC policy applies to all failing mail.
✓ Aggregate reports enabled #19

Aggregate reports are sent to: mailto:rua@duo.nl
✓ Subdomain policy: reject #20

Subdomains are covered by policy 'reject'.
✓ Report addresses in own domain #29

All report addresses are in your own organizational domain.

DKIM

warn

Selectors: selector1, selector2

Found

Selectors: selector1, selector2
_domainkey: NOERROR

Selector	Key	Flags
selector1	RSA 1024 bits
selector2	RSA 1024 bits

Checks

✓ Keys found: selector1, selector2 #7

DKIM keys found for this domain with selectors: selector1, selector2
!

1024-bit DKIM key

1024-bit RSA keys are the minimum and are considered weak today: selector1 (1024 bits), selector2 (1024 bits). Rotate to a 2048-bit key.

#23
✓ No problematic flags #24

No keys in test mode, revoked, or limited to SHA-1.

DNSSEC

warn

Signed, DS published at parent

Found

DNSKEY records: Yes (3)
DS at parent: Yes
Algorithms: RSASHA256 (8)
Key tags: 14711, 30434, 20343
Signatures valid until: 25 October 2026, 16:55 UTC

Checks

✓ Signed, DS published at parent #8

DNSSEC is enabled for this domain (DNSKEY and DS present), providing additional security for DNS lookups.
!

Signatures expire in 92h0m0s

DNSKEY signatures expire at 2026-10-25T16:55:32Z (in 92h0m0s). Check that re-signing works.

#21

MX

pass

2 mail servers

Found

Priority	Host	Records	Reverse DNS
10	grnms101.duo.nl	A 194.171.77.166 AAAA 2001:67c:262c:860::166	grnms101.duo.nl ✓ grnms101.duo.nl ✓
10	grnms102.duo.nl	A 194.171.77.167 AAAA 2001:67c:262c:860::167	grnms102.duo.nl ✓ grnms102.duo.nl ✓

Checks

✓ 2 MX records #9

Found 2 MX records for this domain.
✓ All hosts resolve #10

All MX records resolve to valid IP addresses.
✓ All hosts have IPv6 #11

All MX records resolve to IPv6 addresses.
✓ Redundant MX hosts #12

Found 2 MX records, which provides redundancy for email delivery.
✓ At most 5 MX records #13

Found 2 MX records, which is within the recommended range (1-5).
✓ No localhost targets #14

No MX records pointing to localhost found.
✓ No private IP addresses #15

No MX records resolving to private IP addresses found.
✓ No CNAME targets #22

No MX records point to a CNAME.
✓ Reverse DNS confirmed #30

All 4 MX addresss have a PTR record that resolves back to them.

TLS

warn

no MTA-STS · no TLS-RPT · DANE on 2 of 2 MX hosts

Found

DANE (TLSA records)

MX host	TLSA	DNSSEC
grnms101.duo.nl	3 1 1 3d93eae8c1a6f279…	Yes
grnms102.duo.nl	3 1 1 3d93eae8c1a6f279…	Yes

Checks

!

Not configured

MTA-STS is not configured, so other mail servers fall back to unencrypted delivery when TLS fails or is stripped by an attacker. Publish a _mta-sts TXT record and a policy at https://mta-sts.<domain>/.well-known/mta-sts.txt.

#32
!

Not configured

MTA-STS or DANE is used without TLS-RPT, so you get no reports when senders fail to deliver because of TLS problems. Publish _smtp._tls TXT "v=TLSRPTv1; rua=mailto:...".

#35
✓ DANE on all MX hosts #36

All 2 MX hosts publish DNSSEC-validated TLSA records.

BIMI

info

No BIMI record

Checks

i

Not configured

BIMI shows your logo next to your mail in supporting mail clients. It requires DMARC enforcement.

#38