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Compare resolvers worldwide and inspect returned answers.
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Email authentication
Tools to verify and validate your email authentication setup.
Deliverability
Email deliverability audit
Audit MX, SPF, DKIM and DMARC to confirm a domain is ready to send.
Mail header analyzer
Decode participants, authentication results and routing from raw headers.
Email tester
Send a test email and get instant authentication and deliverability feedback.
IP Blacklist Checker
Check if your IP is on email blacklists
Domain Blacklist Checker
Check if your domain is on URI blacklists
SPF Flattener
Flatten SPF records to reduce DNS lookups below the 10-lookup limit.
DKIM Selector Finder
Auto-discover all DKIM selectors for a domain via DNS brute-force.
SMTP/MX Tester
Test SMTP connectivity of your MX servers: banner, STARTTLS, TLS certificate, open relay.
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Detect your IPv4/IPv6 addresses and their geolocation.
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Resolve a PTR record and validate DNS consistency.
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Identify the owner of an IP range and its contacts.
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Calculate network, broadcast and usable hosts for any IPv4 block.
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Calculate IPv6 subnets, address ranges and reverse DNS entries.
Text
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Text case converter
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Encode or decode any content in Base64 without leaving the browser.
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BIMI logos, VMC/CSR certificates and web page diagnostics.
BIMI logo lookup
Inspect a BIMI logo URL - format, metadata and live rendering - before rollout.
BIMI SVG converter
Convert any SVG to BIMI-compliant Tiny-PS format in seconds.
CSR parser
Inspect a CSR, extract subject details, fingerprints and requested SANs.
VMC inspector
Inspect a Verified Mark Certificate - issuer, validity and SAN coverage - before you publish BIMI.
Page size checker
Check if your page exceeds Google's 2 MB crawl limit.
Phishing URL Checker
Check if a URL is flagged as phishing or malware by 4 threat intelligence sources.
t-mobile.com · 🇺🇸 US · communication-services
Scan week: 2026-03-02
global
#681 / 1090
country US
#381 / 506
index sp-500
#379 / 503
index nasdaq-100
#81 / 101
sector communication-services
#30 / 45
Deploy MTA-STS to enforce TLS for inbound email
Add a secondary MX for redundancy
Add a TLS-RPT record to receive TLS failure reports
Enable DNSSEC for your domain to improve DNS security
Each company in the Observatory is analyzed weekly for email authentication standards. The audit provides a comprehensive view of the company's email security posture.
What this page shows:
Q: How is the score calculated?
A: Points are awarded for each standard based on configuration quality, totaling up to 100.
Q: What do the grades mean?
A: A+ is excellent (90-100), F indicates significant gaps (below 50).
| Page | Purpose |
|---|---|
| Observatory Dashboard | Overall overview with key metrics |
| Statistics | Cross-index and cross-sector comparison |
| Email Domain Check | Audit your own domain |