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.
DMARC Record Builder
Fill in the fields below to construct your DMARC policy record.
Percentage of failing messages to apply policy (1-100).
mailto:
Address to receive daily aggregate XML reports.
mailto:
Address for individual forensic failure reports.
Default: 86400 (24 hours).
Generated DMARC Record
Publish this TXT record at
_dmarc.yourdomain.com
Frequently Asked Questions
What is a DMARC record?
DMARC (Domain-based Message Authentication, Reporting & Conformance) is an email authentication protocol that builds on SPF and DKIM. A DMARC record is a DNS TXT record that tells receiving mail servers how to handle emails that fail authentication.
Why do I need DMARC?
DMARC protects your domain from spoofing, phishing, and unauthorized use. It also provides reports that give visibility into who is sending email on behalf of your domain, helping you monitor and improve email deliverability.
What does the "policy" (p) tag mean?
none: No action, monitoring only. quarantine: Mark failed emails as spam. reject: Block delivery entirely. Start with none and move to reject after analyzing reports.
What is the difference between rua and ruf?
rua sends aggregate XML reports daily showing all authentication results. ruf sends detailed forensic reports on individual failures (may contain sensitive content). Both are optional.
How do alignment modes (adkim/aspf) work?
Relaxed (r) allows partial domain matches (e.g., subdomain). Strict (s) requires exact domain match between the header from address and DKIM signing domain / SPF envelope domain. Relaxed is usually sufficient.
What does pct (percentage) do?
The pct tag applies the policy only to a percentage of failing messages (1-100). Useful for gradual rollout. Default is 100.
What is the subdomain policy (sp)?
If you want subdomains to have a different policy than the main domain, you can specify it using sp. If not set, the main policy applies to all subdomains.
How do I publish the generated record?
Create a TXT record in your DNS with the hostname _dmarc.yourdomain.com (replace yourdomain.com). The value is the string generated by this tool.
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.
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.
DNS Record Lookup - Online Query A, AAAA, MX, TXT
Query DNS records for any domain directly from your browser using DNS-over-HTTPS. See A, AAAA, MX, CNAME, and TXT. No logs.
DNS Propagation Checker - Online Verify Record Status
Query a domain's DNS record against multiple public resolvers (Google, Cloudflare) and see how it propagates. Client‑side fetch.
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.
Email Header Analyzer - Online SPF, DKIM, DMARC Check
Paste raw email headers and see authentication results (SPF, DKIM, DMARC) in a readable table. Find spoofing attempts.
DNSSEC Chain Validator - Online Check RRSIG & DS
Validate a DNSSEC chain by entering DS and RRSIG records. Verify that signatures match. Educational. Local algorithm.
DNS Record Syntax Checker - Online Validate BEFORE Publishing
Paste any DNS record and check if its format is valid for the selected record type (A, AAAA, CNAME, MX, TXT, SRV). Prevents typos.
CAA Record Generator - Online DNS Certification Authority
Create a CAA DNS record to specify which certificate authorities can issue SSL certs for your domain. Prevent mis‑issuance.
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.
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.
What Are My DNS Servers - Online Detect via Browser
Attempt to detect your current DNS resolver IPs using DNS‑leak test queries. Educational. Privacy‑friendly.
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.
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.
DNS Lookup - Online Domain Records Checker (A, MX, CNAME)
Query DNS records for any domain directly from your browser using DNS-over-HTTPS. See A, AAAA, MX, CNAME, and TXT records. No logs.