Postmark API integration, DNS configuration, and transactional email deliverability.
1 article
Detailed technical guide for developers: DNS configuration (DKIM, custom Return-Path), REST API vs SMTP, Message Streams, dedicated IP, webhooks and 2026 pricing.
DNS Lookup
Choose a DNS record type to search for.
Propagation & diagnostics
Compare resolvers worldwide and inspect returned answers.
Keep history, monitor your zones and automate recurring checks.
Email authentication
Tools to verify and validate your email authentication setup.
Deliverability
Email deliverability audit
Audit MX, SPF, DKIM and DMARC to confirm a domain is ready to send.
Mail header analyzer
Decode participants, authentication results and routing from raw headers.
Email tester
Send a test email and get instant authentication and deliverability feedback.
IP Blacklist Checker
Check if your IP is on email blacklists
Domain Blacklist Checker
Check if your domain is on URI blacklists
SPF Flattener
Flatten SPF records to reduce DNS lookups below the 10-lookup limit.
DKIM Selector Finder
Auto-discover all DKIM selectors for a domain via DNS brute-force.
Text
Transform, encode and measure your content in seconds.
Text case converter
Convert any block of text to upper or lower case instantly.
Base64 encoder / decoder
Encode or decode any content in Base64 without leaving the browser.
Slug generator
Transform any sentence into an SEO-friendly slug in seconds.
Word & character counter
Measure the length of any text, with instant word and character counts.
Web & Certificates
BIMI logos, VMC/CSR certificates and web page diagnostics.
BIMI logo lookup
Inspect a BIMI logo URL - format, metadata and live rendering - before rollout.
CSR parser
Inspect a CSR, extract subject details, fingerprints and requested SANs.
VMC inspector
Inspect a Verified Mark Certificate - issuer, validity and SAN coverage - before you publish BIMI.
Page size checker
Check if your page exceeds Google's 2 MB crawl limit.
IP
Look up addresses, owners, reverse records and ranges.