Free Outbound Engineering, DNS & Deliverability Tools
Real-time DNS validators, RFC 5321 SMTP socket probes, 29-zone blacklist monitors, and open-source AI copy generators. Zero registration, zero API keys, and instant feedback.
⭐ Featured Outbound Utilities
Most frequently used deliverability & authentication toolsFree SPF Record Checker & RFC 7208 10-Lookup Limit Validator
Check your domain’s SPF record in real-time. Validate syntax, verify mechanism formatting, and check the strict RFC 7208 10-DNS-lookup limit to prevent PermError bounces.
Free Email Verifier Tool: Verify Mailbox Existence, Syntax & SMTP Handshake
Verify any email address in seconds for free. Run multi-stage checks: RFC 5322 syntax validation, MX record discovery, disposable domain blacklist check, and safe SMTP handshake verification.
Free Blacklist Checker: Scan 29 Real-Time DNSBL Zones for IP & Domain Reputation
Check if your sending IP address or domain is blacklisted. Concurrently queries 29 authoritative DNSBL registries including Spamhaus ZEN, Barracuda, Spamcop, and SORBS.
🎯 Guided Engineering Playbooks
Step-by-step tool workflows for common outbound objectivesNew Cold Domain Genesis
Configure brand-new secondary sending domains with pristine authentication before launching initial warm-up campaigns.
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Confirm domain registration age & check for prior abuse flags.
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Generate strict RFC 7208 syntax without exceeding the 10-lookup cap.
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Create cryptographic public/private keypair for PowerMTA/Postfix.
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Enforce quarantine/reject alignment & connect aggregate reporting (RUA).
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Calculate safe daily send limits across your sending node cluster.
Spam Box Emergency Rescue
Diagnose sudden open-rate drops, locate DNSBL blacklist listings, and inspect message headers for RFC violations.
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Scan Spamhaus, Barracuda, and SORBS across IP & sending domain.
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Scan body copy for 400+ spam keywords and spam-filter flags.
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Inspect Received: transit hops, TLS ciphers, and relay delays.
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Simulate deliverability routing across Google, Microsoft, and Yahoo.
High-Converting Outbound Engine
Clean your prospect list with real-time SMTP handshakes, inject dynamic Spintax variation, and generate high-reply copy.
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Run zero-bounce SMTP handshakes and purge invalid mailboxes.
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Create thousands of unique variations to bypass ESP duplicate fingerprinting.
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Craft 10 high-converting hooks with predicted open rates.
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Simulate realistic prospect objections and reply handles autonomously.
📂 Complete Engineering Directory
Browse all 49 production toolsFree SMTP Server Test Tool: RFC 5321 Client/Server Conversation Inspector
Connect to SendGrid, Mailgun, Amazon SES, or any custom SMTP server and watch the exact client/server conversation in real-time. Diagnose authentication (535), relay rejection (550), and TLS cipher blocks.
Free SPF Record Checker & RFC 7208 10-Lookup Limit Validator
Check your domain’s SPF record in real-time. Validate syntax, verify mechanism formatting, and check the strict RFC 7208 10-DNS-lookup limit to prevent PermError bounces.
Free SPF Record Generator: Step-by-Step DNS Builder & Syntax Optimizer
Generate a clean, RFC-compliant SPF TXT record in seconds. Select your mail relays, add dedicated PowerMTA IPs, configure softfail/hardfail policies, and copy formatted DNS records.
Free DKIM Record Checker: Verify Selector, Public Key & Cryptographic Alignment
Check your domain’s DKIM DNS record in real-time. Verify selector resolution, parse 1024-bit vs 2048-bit RSA public keys, and ensure compliance with Google and Yahoo sender rules.
Free DKIM Generator: Generate 2048-Bit RSA Keypair & Formatted DNS Record
Generate a cryptographically secure 2048-bit RSA DKIM keypair in seconds. Download your private key for PowerMTA or Postfix, and copy the formatted DNS TXT public key record.
Free DMARC Record Checker: Audit Policy, Alignment & Reporting Compliance
Check your domain’s DMARC record in real-time. Verify policy enforcement (p=reject, quarantine, none), parse aggregate reporting (rua) tags, and ensure compliance with Google and Yahoo 2026 rules.
Free DMARC Generator: Step-by-Step Policy Builder & DNS Wizard
Generate a compliant DMARC record in seconds. Select policy enforcement (none, quarantine, reject), configure aggregate reporting mailboxes, set alignment strictness, and copy formatted DNS records.
Free CNAME Record Checker: Verify Alias Resolution, CDN & Tracking Domains
Check your domain’s CNAME records in real-time. Verify custom email tracking domains, CDN aliases, and subdomains to prevent broken links and tracking failures in cold outreach.
Free Email Verifier Tool: Verify Mailbox Existence, Syntax & SMTP Handshake
Verify any email address in seconds for free. Run multi-stage checks: RFC 5322 syntax validation, MX record discovery, disposable domain blacklist check, and safe SMTP handshake verification.
Free ESP Checker: Identify Destination Mailbox Provider & Sending Rules
Instantly identify the Email Service Provider (ESP) or Secure Email Gateway (SEG) behind any domain or email list. Detect Google Workspace, Microsoft 365, Proofpoint, and Mimecast.
Free Blacklist Checker: Scan 29 Real-Time DNSBL Zones for IP & Domain Reputation
Check if your sending IP address or domain is blacklisted. Concurrently queries 29 authoritative DNSBL registries including Spamhaus ZEN, Barracuda, Spamcop, and SORBS.
Free SSL Checker: Inspect Certificate Expiration, SANs & TLS Protocol Security
Check any domain’s SSL/TLS certificate in real-time. Inspect expiration dates, verify Subject Alternative Names (SANs), review the issuer and signature algorithm, and see the protocol and cipher actually negotiated.
Free WHOIS Domain Checker: Look Up Domain Age, Registrar & Deliverability Risk
Check the WHOIS & RDAP registration details of any domain. Inspect exact domain age, registrar identity, expiration dates, nameservers, and calculate cold email deliverability risk tiers.
Free Inbox Placement Test: Simulate Spam Filter Routing & Inbox Ratios
Simulate and test your email inbox placement rate. Score your subject line and your self-reported SPF/DKIM/DMARC posture, rDNS and domain age to estimate primary inbox vs spam placement across Gmail and Microsoft 365.
Free RFC 8058 One-Click List-Unsubscribe Header Generator & 2026 Bulk Sender Grader
Generate RFC 8058 compliant List-Unsubscribe and List-Unsubscribe-Post headers for PowerMTA, KumoMTA, and Postfix. Meet 2026 Google & Yahoo bulk sender mandates.
Free Outbound Email HTML & Tracking Link Sanitizer: Scan Hops, Pixels & Traps
Scan and sanitize outbound email HTML. Detect and strip hidden 1×1 tracking pixels, unmask redirect link hops, and generate clean RFC 2046 plaintext alternatives.
Free Email Deliverability Test – Sender Score Audit
Run a comprehensive 10-pillar deliverability audit on your email sending infrastructure. Audit DNS records, blacklist status, IP warmup curve, and calculate your global sender score.
Free IP Blacklist Checker: Real-Time RBL & DNSBL Reputation Scanner
Check if your mail server IP address is blacklisted on 20+ major DNSBL and RBL registries including Spamhaus ZEN, Barracuda, SpamCop, and SORBS. Includes reverse DNS (PTR) and FCrDNS verification.
Free Domain Blacklist Checker: URIBL, SURBL & Spamhaus DBL Scanner
Check if your domain name or tracking domain is blacklisted on Spamhaus DBL, SURBL, URIBL, and SpamEatingMonkey. Prevent your emails from landing in spam due to domain reputation flags.
Free AI Email Subject Line Generator: 10 High-Converting, Low-Spam Hooks
Generate 10 high-converting cold email subject lines in seconds. Powered by OpenRouter AI: calculates predicted open rates, identifies psychological hooks, and eliminates spam triggers.
Free Cold Email Generator: Craft High-Reply B2B Outreach Drafts with AI
Generate personalized, high-converting cold email drafts in seconds. Powered by OpenRouter AI: uses proven frameworks (PAS, AIDA, BAB) to craft short, conversational emails under 85 words.
Free AI Prompt Generator: Tailored Landing Page & Funnel Prompts
Generate tailored AI mega-prompts for your landing page, sales funnel, or systeme.io Raw HTML in seconds. Engineered for Claude 3.7 / 3.5 Sonnet, ChatGPT GPT-4o, and Gemini with strict conversion constraints and OpenRouter AI.
Free AI Email Generator: 1-Click Cold Email Copywriter for Instant Outreach
Generate a complete, personalized cold email in 1 click. Powered by OpenRouter AI: input your recipient role and core offer to receive a crisp, 60-word sales email ready to send.
Free Cold Email Sequence Generator: Build 4-Step Multi-Touch Outbound Campaigns
Generate a high-reply 4-step cold email sequence in seconds. Powered by OpenRouter AI: crafts the hook, value/case study touch, micro-value follow-up, and graceful break-up email with timing intervals.
Free Cold Email Roaster: Brutal AI Copy Critique, Spam Trigger Audit & Rewrite
Get an unfiltered, cynical critique of your cold email copy. Powered by OpenRouter AI: scores copy effectiveness (1-10), flags spam triggers, and rewrites your message into a punchy 60-word version.
Free LinkedIn Message Generator: Create High-Acceptance Connection Notes & InMails
Generate high-acceptance LinkedIn connection requests (<300 chars), welcome InMails, and follow-ups. Powered by OpenRouter AI: crafts natural, pitch-free outreach messages.
Free Spintax Generator: Inject Dynamic Spintax & Test Variations Instantly
Inject dynamic spintax into your cold emails with AI. Generate millions of unique message variations to bypass spam filters, and test random spun outputs in real-time.
Free Email Spam Checker – Trigger Word Scanner
Scan your email copy in real-time for over 400 spam trigger words. Highlights high-risk phrases across Urgency, Money, and Shady Tactics, and calculates your Spam Trigger Risk Score.
Free AI Email Template Generator: Design Responsive HTML Newsletters & Outreach Drafts
Design production-ready, mobile-responsive HTML email templates in seconds using AutoSMTP AI. Bulletproof table-based layouts compatible with Gmail, Apple Mail, and Outlook with real-time preview and instant HTML export.
Free AI Agent ROI Calculator: Calculate Savings & Pipeline Lift vs Human SDRs
Calculate how much your company will save by deploying autonomous AI SDR agents. Compare fully burdened human SDR salaries, software licenses, and output capacity with automated AI infrastructure.
Free Sales Forecast Tool: Model Outbound Email Volume to Closed-Won ARR
Predict your outbound cold email pipeline and revenue outcomes. Model delivery rates, open rates, reply percentages, meeting conversion rates, and closed-won ARR in real-time.
Free Buyer Persona Generator: Build ICP Dossiers, Pain Points & Hooks with AI
Generate a comprehensive Ideal Customer Profile (ICP) and buyer persona dossier with AI. Powered by OpenRouter: uncovers decision-maker titles, urgent pain points, buying triggers, and cold email hooks.
Free Email Finder Tool: Corporate Email Permutator & Deliverability Probe
Find and verify business email addresses in seconds. Generate standard corporate permutations (first.last, first, flast) and test deliverability against authoritative domain MX servers.
Free Company Size Estimator – AI Headcount Tiers
Estimate employee headcount tiers with AI for any company domain. Powered by OpenRouter AI: tier bands, sales org sizing heuristics, and safe cold outreach volume limits.
Free AI SDR Simulator: Experience Autonomous Outbound Sales Conversations
Experience an autonomous AI SDR agent in real-time. Converses, qualifies leads, handles sales objections, and discusses email deliverability and MTA infrastructure using OpenRouter AI.
Free Email Signature Generator: Build Clean, Deliverability-Safe HTML Signatures
Build a clean, modern, deliverability-safe email signature in seconds. Formats clean inline CSS tables without bloated scripts or spam triggers, ready to copy into Gmail, Outlook, or MailWizz.
Free Email GIF Generator: Create Personalized Animated Visuals for Outreach
Generate personalized animated visuals for your sales outreach. Create lightweight, attention-grabbing animated text cards that boost reply rates in follow-up sequences.
Free DNS Validator & Email Records Audit Tool
Audit a sending domain’s complete email DNS stack in one click: MX, SPF, DKIM, and DMARC with evidence-backed pass, warning, and failure verdicts.
Free Domain Security Scanner & Email Health Scorecard
Run a comprehensive email-domain security audit and receive a transparent 0 to 10 configuration score with a prioritized remediation action checklist.
Free BIMI Record Checker & SVG Logo Validator
Verify a domain’s published BIMI DNS record, test SVG Tiny P/S logo accessibility, inspect VMC certificates, and validate required DMARC enforcement.
Free BIMI Record Generator & Visual DNS Builder
Generate a syntactically valid BIMI TXT record with custom selector, HTTPS SVG Tiny P/S logo URL, and VMC certificate authority in seconds.
Free MTA-STS Checker & TLS Enforcement Tester
Check a domain’s MTA-STS DNS announcement, validate the HTTPS policy file, inspect TLSRPT reporting, and test MX cipher alignment.
Free IP & Domain Reputation Scorecard
Inspect what the public internet sees about your sending IP or domain: forward-confirmed reverse DNS (FCrDNS), PTR consistency, and multi-zone blacklist health.
Free DNS Record Checker & Multi-Type Nameserver Lookup
Look up all DNS record types for a domain—A, AAAA, MX, TXT, NS, CNAME, SOA, and CAA—with live TTL and structured table outputs.
Free Raw SPF Syntax Checker & Offline RFC 7208 Inspector
Paste any raw SPF record string to validate syntax, mechanisms, qualifiers, CIDR IP notation, and the RFC 7208 10-lookup count—before publishing to DNS.
Free Email Header Analyzer & RFC 5322 Transit Inspector
Paste raw email headers to trace MTA transit hops, transmission delays, SPF/DKIM/DMARC verdicts, sender IPs, and spam score heuristics.
Free Email Marketing ROI Calculator: Calculate List Value, Profit & ESP Yield
Calculate true email marketing ROI in seconds. Model list size, open rates, CTR, conversion rates, and AOV against escalating commercial ESP contact tiers vs flat-rate unmetered AutoSMTP bare-metal clusters.
Free Outbound Mailbox Calculator & Domain Ramp Planner
Plan how many sending mailboxes and secondary domains you need for target outbound volume, meeting goals, ESP mix, and safe daily send caps.
Free Sales Commission Calculator & OTE Tier Planner
Model sales compensation and commission structures: base salary, On-Target Earnings (OTE), quota attainment tiers, and performance accelerators.
What does delay keep costing you?
Move the slider, then compare mailbox cost against the pipeline your inboxes are supposed to create.
1x Dedicated Bare-Metal Node with 4x Clean Dedicated IPv4s, automated gas-pedal IP warming, in-band 550 bounce suppression, and custom rDNS/PTR alignment.
🛡️ Agency Verified Deliverability Badge
Showcase verified RFC standards and pristine inbox placement on your agency footer, proposals, or client reporting dashboard.
Need Automated High-Volume Sending Infrastructure?
Free tools help you audit and optimize individual DNS records, but sustained enterprise email delivery requires dedicated physical hardware. AutoSMTP replaces fragile shared relays with private bare-metal PowerMTA and KumoMTA clusters configured automatically in 15 minutes.
Turnkey Dedicated Bare-Metal Clusters
Provisions fully licensed PowerMTA and KumoMTA clusters on enterprise bare-metal with flat predictable pricing and zero third-party markups.
Automated Gas-Pedal IP Warming
Monitors Google Postmaster spam ratios (<0.10%) and real-time deferrals across clean IPv4 subnets to scale daily send limits safely without spam flags.
Native FBL & Socket Interceptors
RFC 5321 in-band 550 bounce suppression and automated Yahoo/Outlook Complaint Feedback Loop ingest to protect sender reputation automatically.
Fully Managed DNS & Auth
Pre-configured dedicated rDNS/PTR, SPF syntax alignment, automatic 2048-bit DKIM key rotation, strict DMARC (p=reject), and verified BIMI integration.
Domain Comparison Matrix
| Deliverability Metric | Domain A | Domain B |
|---|---|---|
| RFC 7208 SPF Lookups | 3 / 10 (Pristine) | 8 / 10 (Near Cap) |
| DKIM Cryptographic Key | 2048-Bit RSA Aligned | 2048-Bit RSA Aligned |
| DMARC Enforcement Policy | p=reject (Strict) | p=none (Audit Only) |
| 34-Zone DNSBL Reputation | 0 / 34 Listings | 0 / 34 Listings |
| Domain Age / Risk Tier | 5+ Years (Established) | 28 Days (Warming Required) |
| Recommended Outbound Action | Safe for transactional | Enforce p=quarantine + ramp 25/day |
Fleet Deliverability Matrix
| Domain | SPF Lookups | DKIM (2048-Bit) | DMARC | DNSBL (34 Zones) | Fleet Grade |
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Inbound Seed Probe Results
5-Pillar Health Scorecard
Domain authentication is fully compliant with Google & Yahoo 2026 sender requirements. Zero DNSBL flags detected across 34 registries.
SPF Lookup Command
curl -s "https://autosmtp.io/api/dns/spf?domain=example.com"
Quick Spintax Tester
Production MTA Directives & Backoff Policies
# Loading configuration...