Email tools
SPF, DKIM, DMARC, mail servers and blocklist reputation — the four things that decide inbox placement.
Email deliverability check
Check whether a domain is set up to send email that arrives: mail servers, SPF record, DKIM selectors and DMARC policy.
Email header analyzer
Paste raw email headers to see every server the message passed through, the delay at each hop, and whether it passed SPF, DKIM and DMARC.
Blacklist check
Query ten major DNS blocklists — Spamhaus, SpamCop, Barracuda and others — to see whether a mail server IP is listed.
Other categories
Reference
Look something up without running a check.
HTTP status codes
What 301, 403, 502 and the rest actually mean, and how to fix them.
Common ports
What listens on each port and whether it should ever face the internet.
Browser errors
ERR_CONNECTION_REFUSED, NXDOMAIN, SSL errors — decoded.
DNS record types
A, MX, TXT, CNAME and friends, with real examples.
Developer utilities
Subnet, cron, base64, JWT, hashes — private, in your browser.