13 Free Tools for Bulletproof Email Deliverability.
Audit your entire sending pipeline end-to-end before pressing send: check MX, SPF, DKIM, and DMARC in one go, build RFC-compliant DNS records, rewrite spam-risk copy and subject lines, and screen disposable domains cleanly.
MX Record Lookup
Inspect inbound mail servers, host priority rankings, and authoritative IPv4/IPv6 resolution in real time to verify failover routing.
DMARC Record Checker
Audit published domain DMARC records, aggregate reporting endpoints (rua), alignment modes, and enforcement grades.
DMARC Record Generator
Generate syntax-valid DMARC TXT policies (p=none, quarantine, reject) with strict domain checks, §7.1 cross-domain reporting alerts, and DNS guides.
BIMI Record Checker
Verify domain eligibility to display your brand logo and blue verified checkmark in Gmail, Yahoo, and Apple Mail across DMARC, SVG Tiny-PS, and VMC PEM.
DKIM Key Inspector
Inspect public DKIM keys, verify 2048-bit RSA key strength against 1024-bit deprecation, and probe selector DNS entries across mail streams.
SPF Record Validator
Validate authorized sending IPs and include chains, catch duplicate-record PermErrors, and track usage against the RFC 7208 10-lookup ceiling.
SPF Record Generator
Build compliant SPF TXT records with presets for Google Workspace, Microsoft 365, SendGrid, and AWS SES while counting recursive DNS lookups.
Spam Word Checker & Cleaner
Inspect email drafts across 170+ filter phrases, leetspeak obfuscation (fr33/c@sh), currency & % off claims, ALL-CAPS shouting, risky links, and Flesch readability.
Email Subject Line Tester
Grade subject lines and preview text for 35-char mobile / 68-char desktop cutoff, fake Re:/Fwd: prefixes, bracket tags, grapheme emojis, and preheader synergy.
Email Spam Audit
Score complete subject-and-body drafts before launching outreach sequences, tracking readability grade level, link load, and spam-filter penalties.
Disposable Email Checker
Detect burner domains using registry lookup, heuristic naming analysis, multi-part TLD parsing, RFC 7505 Null MX checks, and A-record fallbacks.
Email List Cleaner & Scrubber
Upload prospect CSVs or paste lists locally in your browser to deduplicate addresses, remove disposable domains, flag role accounts, and export clean CSVs.
Email Header Analyzer
Trace chronological MTA relays from raw email headers in your browser, uncover transit delays between hops, and inspect SPF/DKIM/DMARC authentication results.
The 4 Pillars of Modern Deliverability.
Primary inbox placement takes more than a valid domain. Audit authentication protocols, build verified brand logos, refine copy & subjects, and scrub high-risk recipients across all four stages.
Authenticate & Protect
Verify gateway priorities, 2048-bit RSA DKIM keys, and strict RFC 7489 DMARC records—plus build error-free SPF and DMARC TXT records with §7.1 validation.
Brand Trust & Identity
Confirm DMARC enforcement eligibility, inspect SVG Tiny-PS logo structure and 1:1 viewBox geometry, and verify VMC PEM certificates for verified inbox avatars.
Subject & Copy Optimization
Preview mobile cutoff truncation, catch fake Re: prefixes, rewrite obfuscated or promotional spam triggers in 1 click, and check Flesch readability.
Hygiene & Route Forensics
Catch throwaway domains, Null MX hosts, and heuristic burner patterns, scrub bulk CSV lists, and inspect chronological MTA relay latencies.
Google, Yahoo & Apple Deliverability Mandates.
Major mailbox providers enforce strict domain, copy, and list-hygiene standards. Audit every requirement across Sortwell's free diagnostics:
Publish a syntax-valid v=DMARC1 policy via the DMARC Generator and advance from p=none to p=quarantine or p=reject with aligned SPF/DKIM.
Confirm your selectors publish 2048-bit RSA keys instead of deprecated 1024-bit keys using the DKIM Key Inspector.
Avoid RFC 7208 PermErrors by staying strictly under 10 DNS lookups as you compose or audit include chains.
Pair DMARC enforcement with SVG Tiny-PS logos & VMC certificates, scrub disposable/Null-MX domains, and eliminate spam triggers.
Common Deliverability Questions.
Everything you need to know about Sortwell's 13 free tools, protocol validation, browser privacy, and live SMTP verification.
What tools are included in the Sortwell Diagnostic Suite?
Sortwell includes 13 specialized tools across three workflows: DNS & Authentication (MX Lookup, DMARC Checker, DMARC Generator, BIMI Checker, DKIM Inspector, SPF Validator, SPF Generator), Content & Copy (Spam Word Checker & Cleaner, Subject Line Tester, Email Spam Audit), and List Hygiene & Forensics (Disposable Email Checker, Email List Cleaner, Email Header Analyzer).
Are all 13 diagnostics free, and is my copy or list stored?
Yes. Every tool is 100% free with no account or credit card required. Copy linters, subject simulators, record generators, CSV scrubbers, and header parsers run locally inside your browser without storing your text or contacts, while DNS/BIMI/MX lookups query authoritative public records in real time.
How is domain DNS auditing different from Sortwell mailbox verification?
DNS tools verify your sending domain foundation (MX, SPF, DKIM, DMARC, and BIMI) so mailbox providers trust your infrastructure. Sortwell's core app connects directly to recipient mail servers via live SMTP verification to check whether an individual recipient mailbox actually exists and accepts mail before you send.
In what order should I use these tools before launching a campaign?
First verify your domain foundation with SPF, DKIM, DMARC, and BIMI tools. Next test your subject line and email body with the Subject Line Tester and Spam Word Cleaner. Finally, screen signups or exports using the Disposable Email Checker and List Cleaner.
Clean your entire email list with zero bounces.
Sortwell checks addresses the way a mail server would — live SMTP handshake, syntax, MX verification, and spamtrap detection.