cdu.de

Checked 21 October 2026, 22:06 UTC · via 8.8.8.8
!Passed with warnings
24 passed 5 warnings 0 failed 3 info

SPF

pass

SPF record published

Found

Record
v=spf1 ip4:193.219.105.0/24 ip4:87.129.40.18 ip4:87.129.40.20 ip4:87.129.40.21 ip4:87.129.40.22 include:spf.protection.outlook.com include:inxserver.com include:spf.mailjet.com include:spf.sendinblue.com mx -all
DNS lookups
6 of 10
Void lookups
0 of 2

Checks

  • ✓ No deprecated ptr mechanism #1
    No ptr mechanism found in SPF record.
  • ✓ 6 of 10 DNS lookups #2
    SPF record needs 6 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

pass

p=reject (_dmarc.cdu.de)

Found

Record
v=DMARC1; p=reject; sp=reject; rua=mailto:dmarc@mailinblue.com!10m, mailto:dmarc@ubgnet.de!10m; ruf=mailto:dmarc@mailinblue.com!10m, mailto:dmarc@ubgnet.de!10m; rf=afrf; pct=100; ri=86400
Found at
_dmarc.cdu.de
External report address
mailto:dmarc@mailinblue.com!10m (authorized)
External report address
mailto:dmarc@ubgnet.de!10m (authorized)
TagValueMeaning
vDMARC1Version
prejectPolicy
sprejectSubdomain policy
pct100Percentage of mail the policy applies to
ruamailto:dmarc@mailinblue.com!10m, mailto:dmarc@ubgnet.de!10mAggregate report addresses
rufmailto:dmarc@mailinblue.com!10m, mailto:dmarc@ubgnet.de!10mFailure report addresses
rfafrfFailure report format
ri86400Report interval (seconds)

Checks

  • ✓ Policy: reject #4
    DMARC policy is set to 'reject', which provides the strongest protection against email spoofing.
  • ✓ 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@mailinblue.com!10m, mailto:dmarc@ubgnet.de!10m
  • ✓ Subdomain policy: reject #20
    Subdomains are covered by policy 'reject'.
  • ✓ External report addresses authorized #29
    Report addresses in other domains have published their authorization.

DKIM

warn

Selectors: mail, selector1

Found

Selectors
mail, selector1
_domainkey
NOERROR
SelectorKeyFlags
mailRSA 1024 bits
selector1RSA 2048 bits

Checks

  • ✓ Keys found: mail, selector1 #7
    DKIM keys found for this domain with selectors: mail, selector1
  • !
    1024-bit DKIM key
    1024-bit RSA keys are the minimum and are considered weak today: mail (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

Not signed

Found

DNSKEY records
No (0)
DS at parent
No

Checks

  • !
    Not enabled
    DNSSEC is not enabled for this domain. Consider enabling DNSSEC to protect against DNS spoofing attacks.
    #8

MX

warn

1 mail server

Found

PriorityHostRecordsReverse DNS
5mail48.cdu.deA 193.219.105.48mail48.cdu.de ✓

Checks

  • ✓ 1 MX record #9
    Found 1 MX records for this domain.
  • ✓ All hosts resolve #10
    All MX records resolve to valid IP addresses.
  • !
    Hosts without IPv6
    The following MX hosts could not be resolved to IPv6 addresses: mail48.cdu.de
    #11
  • !
    Single MX host, no backup
    Only one MX record found. For better email reliability, consider adding at least one backup MX server.
    #12
  • ✓ At most 5 MX records #13
    Found 1 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 1 MX address have a PTR record that resolves back to them.

TLS

warn

no MTA-STS · no TLS-RPT · DANE on 0 of 1 MX hosts

Found

DANE (TLSA records)

MX hostTLSADNSSEC
mail48.cdu.denone-

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
  • i
    Not configured
    TLS-RPT lets senders report TLS delivery problems to you. It is most useful together with MTA-STS or DANE.
    #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