Mail domain report: sron.nl

SPF

pass

SPF record published

Found

Record: v=spf1 mx ip4:192.87.212.29 ip4:192.87.212.25 ip4:192.87.212.28 ip6:2001:610:1409:231::20 ip6:2001:610:1409:231::21 include:spf.protection.outlook.com ~all
DNS lookups: 2 of 10
Void lookups: 0 of 2

Checks

✓ No deprecated ptr mechanism #1

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

SPF record needs 2 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.sron.nl)

Found

Record: v=DMARC1; p=quarantine; rua=mailto:dmarc-rua@sron365.onmicrosoft.com; ruf=mailto:dmarc-ruf@sron365.onmicrosoft.com; fo=1
Found at: _dmarc.sron.nl
External report address: mailto:dmarc-rua@sron365.onmicrosoft.com (not authorized)
External report address: mailto:dmarc-ruf@sron365.onmicrosoft.com (not authorized)

Tag	Value	Meaning
v	DMARC1	Version
p	quarantine	Policy
rua	mailto:dmarc-rua@sron365.onmicrosoft.com	Aggregate report addresses
ruf	mailto:dmarc-ruf@sron365.onmicrosoft.com	Failure report addresses
fo	1	Failure reporting options

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:dmarc-rua@sron365.onmicrosoft.com
✓ Subdomain policy: quarantine #20

Subdomains are covered by policy 'quarantine'.
!

Report address not authorized

These report addresses are in another domain that has not agreed to receive your reports, so receivers will not send them: mailto:dmarc-rua@sron365.onmicrosoft.com (needs sron.nl._report._dmarc.sron365.onmicrosoft.com); mailto:dmarc-ruf@sron365.onmicrosoft.com (needs sron.nl._report._dmarc.sron365.onmicrosoft.com). Ask the report provider to publish the record, or check the address.

#29

DKIM

pass

Selectors: selector1

Found

Selectors: selector1
_domainkey: NOERROR

Selector	Key	Flags
selector1	RSA 2048 bits

Checks

✓ Keys found: selector1 #7

DKIM keys found for this domain with selectors: selector1
✓ Strong keys #23

DKIM keys are strong enough: selector1: RSA 2048 bits.
✓ No problematic flags #24

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

DNSSEC

pass

Signed, DS published at parent

Found

DNSKEY records: Yes (1)
DS at parent: Yes
Algorithms: ECDSAP256SHA256 (13)
Key tags: 18299
Signatures valid until: 5 November 2026, 00:00 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 valid until 2026-11-05 #21

DNSKEY signatures are valid until 2026-11-05T00:00:00Z.

MX

warn

3 mail servers

Found

Priority	Host	Records	Reverse DNS
5	mailscanner3.sron.nl	A 192.87.212.25 AAAA 2001:610:1409:231::20	mailscanner3.sron.nl ✓ mailscanner3.sron.nl ✓
10	mailscanner4.sron.nl	A 192.87.212.29 AAAA 2001:610:1409:231::21	mailscanner4.sron.nl ✓ mailscanner4.sron.nl ✓
25	mailscanner5.sron.nl	A 129.125.20.5 AAAA 2001:610:1a08:229:30::110	lookup failed mailscanner2.sron.nl (does not resolve back)

Checks

✓ 3 MX records #9

Found 3 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 3 MX records, which provides redundancy for email delivery.
✓ At most 5 MX records #13

Found 3 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 does not match

The PTR name of these addresses does not resolve back to the same address: 2001:610:1a08:229:30::110 -> mailscanner2.sron.nl.

#30

TLS

warn

MTA-STS testing · no TLS-RPT · DANE on 0 of 3 MX hosts

Found

MTA-STS record: v=STSv1; id=20230815133846Z; rua=mailto:dmarc-rua@sron.nl
Policy URL: https://mta-sts.sron.nl/.well-known/mta-sts.txt
Mode: testing
Allowed MX: mailscanner3.sron.nl, mailscanner5.sron.nl, mailscanner4.sron.nl
Max age: 2419200 seconds

DANE (TLSA records)

MX host	TLSA	DNSSEC
mailscanner3.sron.nl	none	-
mailscanner4.sron.nl	none	-
mailscanner5.sron.nl	none	-

Checks

✓ Record published #32

MTA-STS record found with id 20230815133846Z.
!

Policy in testing mode

With mode: testing, senders only report TLS problems (via TLS-RPT) and still deliver without TLS. Switch to mode: enforce once reports are clean.

#33
✓ All MX hosts covered #34

Every MX host matches an mx: line of the MTA-STS policy.
!

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
i

Not used

No MX host publishes TLSA records. DANE lets senders verify your mail server's certificate through DNSSEC; it requires DNSSEC on the MX host's zone.

#36

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