UD5 Toolkit
SPF Record Validator – Syntax Check & Limit Analyzer
Validate the syntax of an SPF record, check for the 10‑lookup limit, and flatten nested includes. Improve email deliverability by fixing SPF errors.
Email Header Analyzer - Online SPF, DKIM, DMARC Check
📧 Email Header Analyzer
Paste raw email headers to instantly check SPF, DKIM, DMARC, and view key header fields.
Look for the full headers in your email client (Gmail: "Show original", Outlook: "View message source").
Analysis results will appear here.
Frequently Asked Questions
SPF (Sender Policy Framework) validates that the sending server is authorized to send emails on behalf of a domain. A PASS means the email came from a permitted source, reducing spoofing risk.
DKIM (DomainKeys Identified Mail) adds a digital signature to the email header. The receiving server verifies it using the sender's public DNS record. A PASS indicates the message was not altered in transit.
DMARC (Domain-based Message Authentication, Reporting & Conformance) builds on SPF and DKIM. It tells receivers how to handle emails that fail checks (e.g., reject, quarantine) and enables domain owners to get reports.
Gmail: Open the message, click three dots → “Show original”.
Outlook: Open message, File → Properties → “Internet headers”.
Apple Mail: Open message, View → Message → “Raw Source”.
Yahoo: Open message, More → “View raw message”.
Outlook: Open message, File → Properties → “Internet headers”.
Apple Mail: Open message, View → Message → “Raw Source”.
Yahoo: Open message, More → “View raw message”.
“None” means the receiving server did not include authentication results in the headers. This can happen if the sender's domain has no SPF/DKIM/DMARC records, or the email was forwarded and headers were stripped.
Absolutely. All analysis is performed entirely in your browser using JavaScript. No data is ever sent to any server.
Email Subject Line Tester – Preview & Length Check
Type your email subject line and see how it will appear on mobile and desktop inboxes. Checks character limits and flags spammy words for better open rates.
CTR Calculator – Click Through Rate for Ads & Emails
Quickly compute click-through rate from impressions and clicks. Use it to measure ad performance, email campaign effectiveness, or organic search CTR.
Email‑Safe Button Generator – Online Inline CSS Bulletproof
Create colorful, bulletproof HTML buttons for email. Uses VML for Outlook, graceful fallback for others.
HTTP Security Header Checker - Online HSTS, CSP, X-Frame Analysis
Paste response headers string and get a security audit. Check presence and configuration of key security headers. Local analysis.
HTML Email Signature Builder - Online Professional Footer Creator
Create a polished HTML email signature with your photo, links, and company details. Live preview and copy HTML to clipboard. Works with Gmail, Outlook, Apple Mail.
Email Spam Trigger Checker - Online Avoid Spam Filters
Paste your email subject and body. The tool highlights common spam trigger words and gives a risk score. Improve inbox placement.
CORS Header Debugger - Online Check Cross‑Origin Access
Enter a URL and see its CORS headers. Understand why a fetch fails. Check preflight responses. Client‑side debugger.
Markdown to Email HTML - Online Newsletter Template
Write in Markdown and get clean, inline‑styled HTML suitable for emails. Pre‑designed templates included. Local conversion.
HMAC Generator - Online SHA‑256/512 Message Authentication
Create an HMAC (Hash‑based Message Authentication Code) using SHA‑256 or SHA‑512 with a secret key. Verify data integrity. Local.
BIMI Record Generator - Online Brand Logo for Email
Generate a BIMI record to display your verified brand logo in email clients. Includes SVG logo URL and VMC certificate path.
DMARC Record Generator - Online Email Policy Builder
Create a DMARC policy record with percentage, reporting addresses, and alignment mode. Validate and copy the final DNS TXT.
DKIM Record Generator - Online Public Key DNS Entry
Generate a DKIM DNS record from a public key and selector. Check syntax. Improve your domain’s email deliverability.
SPF Record Generator - Online Email Authentication DNS
Build a valid SPF TXT record by selecting mail servers, IPv4/IPv6 ranges, and includes. Validate syntax and get ready‑to‑publish output.
Mailto Link Generator - Online HTML Email Link
Build a complex mailto: link with to, cc, bcc, subject, and body. Get the HTML anchor tag. Local.
Email Obfuscator - Online Protect Address from Bots
Hide your email address from scrapers by encoding it using HTML entities and CSS tricks. Still clickable for real users. Local generator.
Email Permutator - Online Generate All Possible Addresses
Enter a first name and last name, plus a domain, to generate common email address patterns. For finding contacts.
Email Spam Score Checker - Online Newsletter Tester
Paste your email body and subject, and get a spam score based on common trigger words and patterns. Improve your cold outreach.
Gravatar Generator & Checker - Online Email to Avatar
Preview the Gravatar image associated with any email address. Generate the correct Gravatar URL. Handy for avatar debugging.
Email Header Parser - Online Analyze Email Delivery Path
Paste raw email headers and get a human-readable breakdown of the delivery route, authentication results, and delays. Private analysis.
Phishing Email Checker - Online Suspicious Link Analyzer
Paste email headers or body text to quickly spot phishing signs, suspicious domains, and obfuscated links. Educational and private.