nanoPost

The WordPress Email Authority

Tools

Interactive tools built on the same research the nanoPost reviews and reference pages draw from. Every tool links back to the review or reference for context.

Choose a provider

  • SMTP cost calculator — rank SMTP and email-API providers by their cheapest published plan for your monthly volume.
  • Free-tier comparator — filter every provider with a free tier by daily and monthly caps, permanent-vs-trial, branding, and SMTP-or-API access.

Configure sending

  • WP Mail config generator — pick a sending provider and a delivery method (plugin settings, wp-config constants, mu-plugin, functions.php) and get the exact snippet to paste.
  • DNS auth checker — query your domain’s live SPF, DKIM, DMARC, and MX records and score them against Gmail, Yahoo, and Microsoft 365 bulk-sender requirements.
  • SPF merger — merge an existing SPF record with the providers you actually send from. Deduplicates includes, counts DNS lookups against the RFC 7208 ten-lookup limit, and flags overflow before receivers PermError the record.
  • MTA-STS generator — pick a policy mode, paste your inbound MX pattern list, and get the mta-sts.txt policy file, the _mta-sts DNS TXT, and the _smtp._tls TLS-RPT TXT — with placement hints per block. Generated in your browser.

Diagnose a problem

  • SMTP error decoder — paste a bounce message, SMTP error code, or wp_mail_failed output and get the cause, who’s at fault, and the exact fix for WordPress.
  • Header auth visualizer — paste raw email headers and get a visual SPF/DKIM/DMARC/ARC chain with per-hop badges, per-mechanism verdict cards, and a plain-English “what to fix” block for every failure. Parsed entirely in your browser.
  • DMARC XML reader — paste or drop a DMARC aggregate report (XML, .xml.gz, or .zip) and get a plain-English summary of who is sending as your domain and whether it aligns. Parsed entirely in your browser.
  • Spam scorer — paste raw MIME and get a SpamAssassin score plus every rule that fired, translated into WP-shop language with a link to the relevant fix guide.
  • Gmail clipping analyzer — paste an email HTML source and get a byte-weight breakdown by component (inlined CSS, base64 images, comments, tracking pixels) plus a clipping verdict at the ~102 KB Gmail desktop ceiling. Parsed entirely in your browser.

Meet the Gmail and Yahoo bulk-sender floor

  • List-Unsubscribe validator — paste raw email headers and get an RFC 8058 + Gmail/Yahoo bulk-sender compliance verdict: header presence, https URL, one-click POST header, and the SPF/DKIM/DMARC floor. Static; runs in your browser.
  • List-Unsubscribe live tester — fire a real RFC 8058 one-click POST at a List-Unsubscribe endpoint and read what the endpoint returns. The static validator confirms the headers are well-formed; this one confirms the endpoint actually accepts the POST.