mtu.de

Checked 21 October 2026, 23:30 UTC · via 8.8.8.8
✗Problems found
26 passed 2 warnings 1 failed 2 info

SPF

pass

SPF record published

Found

Record
v=spf1 a:mx2-63.mtu.de a:mx0-61.mtu.de a:mx1-63.mtu.de -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

fail

p=none (_dmarc.mtu.de)

Found

Record
v=DMARC1; p=none; rua=mailto:dmarc@mtu.de; ruf=mailto:dmarc@mtu.de; pct=100; adkim=r; aspf=r; fo=1
Found at
_dmarc.mtu.de
TagValueMeaning
vDMARC1Version
pnonePolicy
pct100Percentage of mail the policy applies to
ruamailto:dmarc@mtu.deAggregate report addresses
rufmailto:dmarc@mtu.deFailure report addresses
adkimrDKIM alignment (r = relaxed, s = strict)
aspfrSPF alignment (r = relaxed, s = strict)
fo1Failure reporting options

Checks

  • ✗
    Policy: none (monitoring only)
    DMARC policy is set to 'none', which only monitors but doesn't protect against spoofing. Consider upgrading to 'quarantine' or ideally 'reject'.
    #4
  • ✓ Record published #5
    DMARC record exists for this domain.
  • ✓ Valid syntax #17
    DMARC record syntax is valid.
  • ✓ Aggregate reports enabled #19
    Aggregate reports are sent to: mailto:dmarc@mtu.de
  • ✓ Report addresses in own domain #29
    All report addresses are in your own organizational domain.

DKIM

pass

Selectors: default

Found

Selectors
default
_domainkey
NOERROR
SelectorKeyFlags
defaultRSA 2048 bits

Checks

  • ✓ Keys found: default #7
    DKIM keys found for this domain with selectors: default
  • ✓ Strong keys #23
    DKIM keys are strong enough: default: 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 (2)
DS at parent
Yes
Algorithms
ECDSAP256SHA256 (13)
Key tags
45318, 33124
Signatures valid until
29 October 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 2026-10-29 #21
    DNSKEY signatures are valid until 2026-10-29T00:00:00Z.

MX

warn

3 mail servers

Found

PriorityHostRecordsReverse DNS
10mx0-61.mtu.deA 91.217.214.168mx0-61.mtu.de ✓
10mx1-63.mtu.deA 91.217.214.169mx1-63.mtu.de ✓
10mx2-63.mtu.deA 91.217.214.186mx2-63.mtu.de ✓

Checks

  • ✓ 3 MX records #9
    Found 3 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: mx0-61.mtu.de, mx1-63.mtu.de, mx2-63.mtu.de
    #11
  • ✓ 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 confirmed #30
    All 3 MX addresss have a PTR record that resolves back to them.

TLS

warn

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

Found

TLS-RPT record
v=TLSRPTv1; rua=mailto:tls-rpt@mtu.de

DANE (TLSA records)

MX hostTLSADNSSEC
mx0-61.mtu.denone-
mx1-63.mtu.denone-
mx2-63.mtu.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
  • ✓ Reports enabled #35
    TLS reports are sent to: mailto:tls-rpt@mtu.de
  • 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