cducsu.de

Checked 21 October 2026, 22:06 UTC · via 8.8.8.8
!Passed with warnings
26 passed 5 warnings 0 failed 1 info

SPF

pass

SPF record published

Found

Record
v=spf1 a mx ip4:193.17.243.103/32 ip4:193.17.232.103/32 ip4:193.219.105.0/24 ip4:185.96.12.40/32 ip4:185.96.12.60/32 ip4:185.96.12.64/32 include:spf.crsend.com include:spf.sendinblue.com ~all
DNS lookups
4 of 10
Void lookups
0 of 2

Checks

  • ✓ No deprecated ptr mechanism #1
    No ptr mechanism found in SPF record.
  • ✓ 4 of 10 DNS lookups #2
    SPF record needs 4 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.cducsu.de)

Found

Record
v=DMARC1;p=reject;ruf=mailto:dmarc@cducsu.de;rua=mailto:dmarc@cducsu.de
Found at
_dmarc.cducsu.de
TagValueMeaning
vDMARC1Version
prejectPolicy
ruamailto:dmarc@cducsu.deAggregate report addresses
rufmailto:dmarc@cducsu.deFailure report addresses

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@cducsu.de
  • ✓ 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: mail

Found

Selectors
mail
_domainkey
NOERROR
SelectorKeyFlags
mailRSA 1024 bits

Checks

  • ✓ Keys found: mail #7
    DKIM keys found for this domain with selectors: mail
  • !
    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

4 mail servers

Found

PriorityHostRecordsReverse DNS
50mail1.dbtg.deA 193.17.243.101mail1.dbtg.de ✓
50mail2.dbtg.deA 193.17.232.101mail2.dbtg.de ✓
50mail4.dbtg.deA 193.17.236.101mail4.dbtg.de ✓
500mail3.dbtg.deA 193.17.243.102mail3.dbtg.de ✓

Checks

  • ✓ 4 MX records #9
    Found 4 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: mail1.dbtg.de, mail2.dbtg.de, mail4.dbtg.de, mail3.dbtg.de
    #11
  • ✓ Redundant MX hosts #12
    Found 4 MX records, which provides redundancy for email delivery.
  • ✓ At most 5 MX records #13
    Found 4 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 4 of 4 MX hosts

Found

DANE (TLSA records)

MX hostTLSADNSSEC
mail1.dbtg.de3 1 1 5d0fbd4152c10b28… 3 1 1 e4a974c31420186f…Yes
mail2.dbtg.de3 1 1 8818a2e7d9f70535… 3 1 1 5d0fbd4152c10b28…Yes
mail4.dbtg.de3 1 1 5d0fbd4152c10b28… 3 1 1 3db22ad186cf71fa…Yes
mail3.dbtg.de3 1 1 5d0fbd4152c10b28… 3 1 1 238bfce604e61351…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 4 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