Free tools · 26 and counting
Tools that earn
their keep
The checks, generators and calculators every sender needs — free, no sign-up, and running in your browser. The same care we put into the product, applied to the open web.
DNS & authentication
The records receivers check before they read a word — tested, counted, generated and finally read.
Domain Health Checker
SPF, DKIM, DMARC and MX in one pass, with plain-language fixes.
Open toolSPF Checker
Resolves your whole include tree and counts every DNS lookup against the limit of 10.
Open toolSPF Record Generator
Compose a lean record from your providers with the lookup budget counted live.
Open toolDMARC Record Generator
Build the exact TXT record — policy ladder, reporting and every tag explained.
Open toolDMARC Report Viewer
Open RUA XML (or .gz) and read who sends as your domain — as a table, not XML.
Open toolDKIM Record Checker
Look up a selector and measure the real RSA/Ed25519 key strength with WebCrypto.
Open toolDKIM Generator
Key pair generated in your browser; the private key never leaves your machine.
Open toolDNS Lookup
dig without the terminal: any record type, real TTLs, two resolvers.
Open toolMTA-STS & TLS-RPT Checker
The records and policy file behind enforced-TLS delivery, checked in one pass.
Open toolTesting & analysis
What happened — or what's about to. Forensics and pre-flight checks for every send.
Blocklist Checker
Resolve a domain to its IPs and sweep them across 13 live DNSBLs, with reverse DNS and ASN ownership.
Open toolEmail Header Analyzer
SPF/DKIM/DMARC verdicts, domain alignment and every server hop with its delay.
Open toolEmail Checker
Syntax, live MX, disposable domains, role accounts and typo rescue — honestly scoped.
Open toolSpam Word Checker
Every filter-bait phrase highlighted in place, with an honest density score.
Open toolSubject Line Tester
Eight cold-email checks plus a Gmail-style inbox preview, scored as you type.
Open toolEmail Size Checker
Weigh your HTML against Gmail's 102KB clip before Gmail does it for you.
Open toolDomain intelligence
Reconnaissance on any domain, straight from public registries and transparency logs.
Prospecting & data
Finding people and keeping the data clean — without uploading it anywhere.
Email Permutator
The 14 address patterns companies actually use, ordered by frequency, MX-checked.
Open toolEmail List Cleaner
Dedupe a CSV and drop broken, disposable and role addresses — all in your browser.
Open toolPhone Number Validator
E.164, country and line type from real numbering plans, not a regex.
Open toolCalculators & planning
The math behind outreach decisions, with shareable scenarios.
Cold Email ROI Calculator
Mailboxes and reply rates in, projected meetings and revenue out.
Open toolEmail Warmup Calculator
A day-by-day ramp schedule for new mailboxes, with safety warnings.
Open toolA/B Test Calculator
A real z-test on your variants, plus the sample size you actually need.
Open toolSMS Length Calculator
Segment counting, GSM-7 vs Unicode, and the characters that triple your bill.
Open toolCopy & branding
The words and the look — tuned for replies, not just polish.
The tools check. Norbelys protects.
Everything these tools check once, Norbelys watches continuously on every mailbox and domain you connect.