Tools / SMTPfast
Free email tools for DNS, deliverability, and email debugging.
Check SPF, DKIM, DMARC, and MX records, analyze message headers, scan risky email copy, and preview markdown email templates before you send.
Available tools.
No signup, no project setup, no dashboard required. Open the tool, paste a domain or email, and get a readable result.
SPF Record Checker
Look up SPF TXT records, catch duplicate records, and verify which senders are authorized for a domain.
Use toolDKIM Record Validator
Validate DKIM selectors, public keys, and DNS fallback behavior before a campaign reaches inbox providers.
Use toolDMARC Record Analyzer
Decode DMARC policies, report addresses, alignment settings, and enforcement gaps in plain English.
Use toolMX Record Checker
Inspect mail exchanger records, priorities, and routing risks for any domain receiving email.
Use toolEmail Header Analyzer
Paste raw headers to trace message hops, authentication results, sender IPs, and delivery metadata.
Use toolSpam Content Checker
Review subject lines and email copy for risky patterns, formatting issues, and missing compliance signals.
Use toolMarkdown Email Preview
Turn markdown into a simple email-safe HTML preview and copyable template for transactional messages.
Use toolEmail Address Validator
Validate syntax, MX records, disposable domains, role accounts, and common typos before an address enters your list.
Use toolBIMI Record Checker
Look up BIMI records, validate the logo and VMC tags, and confirm the DMARC enforcement your inbox logo depends on.
Use toolEmail Subject Line Tester
Preview mobile and desktop truncation and catch spam trigger words, all caps, and punctuation that hurt open rates.
Use toolImage Metadata Cleaner
Detect AI provenance (C2PA), EXIF, and XMP in an image and download a clean copy. Runs entirely in your browser.
Use toolEmail Compatibility Checker
Paste your HTML email and see which CSS and HTML features break in Gmail, Apple Mail, Outlook, Yahoo and Samsung Mail, with a fix for each.
Use toolWhy these tools exist.
Authenticate a sending domain
Check SPF, DKIM, DMARC, and MX records from one public hub before you send through SMTPfast or any other provider.
Debug a real delivery problem
Use header analysis and DNS lookups to see where a message came from, which checks passed, and where routing went wrong.
Prepare better email content
Preview markdown email templates and run a lightweight content scan before a transactional or lifecycle email goes live.
Email deliverability checks without a signup wall.
These tools are built for the early debugging work developers do before they need a full email platform: checking DNS, reading provider headers, and testing copy or templates.
Are these email tools free?
Yes. The SPF, DKIM, DMARC, MX, header, spam content, and markdown preview tools are public and free to use.
Do you store pasted headers or email content?
The header analyzer, spam checker, and markdown preview run in your browser. DNS lookups call our API only for the domain record lookup.
Can these tools guarantee inbox placement?
No single checker can guarantee inbox placement. These tools surface common configuration and content issues so you can fix them before sending.
Need more than public checks?
SMTPfast handles sending, domain authentication, delivery events, bounces, suppressions, and analytics from the same dashboard.
Get Started Free