Comparison

Custom SMTP vs Post SMTP.

Both plugins fix WordPress email the same way, and both keep their email log free. The difference is the model again: Post SMTP sells a Pro licence, and several of the answers to “did it arrive?” live behind it. Every claim about Post SMTP below comes from their own pricing page, listing or documentation, checked on 30 July 2026 and linked at the bottom.

Contents sourced & dated

01 · Common ground

Where the two
are identical.

A comparison that opens with the differences is hiding something. These points are settled and equal, and none of them should decide your choice.

  • Both replace unauthenticated server mail with delivery through a provider you configure, which is the actual fix for WordPress email.
  • Both keep the email log free, with search and filtering: on this point Post SMTP is more generous than WP Mail SMTP, and it deserves saying.
  • Both notify you by email when sending fails, in the free version.
  • Both are actively maintained and tested against WordPress 7.0.
  • Both are GPL, installed from WordPress.org, with no account required to send.

02 · The split

The difference
is the model.

Not the quality of either codebase: the decision of what sits in the free plugin and what sits behind a licence.

Post SMTP is the free tier of a commercial product, with licences from $59.99 to $99.99 a year. Their free version is a real tool: the setup wizard, the log, the SPF, DKIM and DMARC checks and the email failure notice cost nothing. But the Amazon SES, Microsoft 365 and Zoho mailers, the open tracking, the alert channels beyond email, the automatic resend of failed messages and the advanced features of their mobile app are Pro.

Custom SMTP has one version. The log, the alerts, the resend, the notification switches and the Amazon SES support are all in the free plugin, and there is no paid edition for them to move to. The trade-off is honest too: a solo maintainer, a smaller install base, no mobile app and no add-on catalogue.

03 · Side by side

Feature by feature,
sourced and dated.

“Pro” means Post SMTP’s paid licence, from $59.99 a year. Sources for every row are at the bottom of the page.

Comparison · 30 July 2026 free means free
Post SMTPCustom SMTP
Send through your SMTP providerFree, 15+ mailersFree, 12 presets + any SMTP server
Amazon SESProFree, API with IAM role, no stored keys
Outlook / Microsoft 365Pro; one-click setup on the Business licenceFree preset, via SMTP
Zoho MailProFree preset
Email logFree; bulk resend and automatic resend are ProFree, with preview, resend and CSV export
Failure alertsFree by email, Chrome extension and mobile app; Slack, Teams, Twilio and webhook are ProFree · email, webhook, admin notice
Volume-spike alertsNot advertisedFree, absolute hourly and daily thresholds
Open trackingProNot offered, by design
Setup wizard, DNS checksFree; SPF, DKIM and DMARC checks built inNo wizard: presets fill the settings, the guides carry the DNS part
Settings locked in codeNot advertisedPHP constants and environment variables, every setting
PriceFree, then $59.99 to $99.99 / yearFree, no paid version

The same Outlook nuance as everywhere on this site: our preset uses SMTP authentication, which Microsoft is retiring in stages for Exchange Online; their Pro mailer uses the Microsoft API and is not affected. The Outlook guide documents the timeline.

04 · Credit where due

What Post SMTP
does better.

An honest comparison has this section, and not as a formality. If these points decide it for you, take their plugin.

  • The mobile app and the Chrome extension. Failure notifications on your phone and in your browser, with the log a tap away: nobody else on this market has that, including us. The app exists in free and Pro flavours.
  • The onboarding. A three-step wizard, one-click OAuth setups for Gmail and Microsoft on the paid tiers, and SPF, DKIM and DMARC checks built into the plugin rather than into documentation.
  • A broader, more modern mailer catalogue. Resend, MailerSend, Mailtrap, Sweego, Emailit and a dozen others ship as connectors; our answer for providers without a preset is generic SMTP.
  • Scale and track record. 300,000+ active installations and 4.7 stars over 524 reviews, with a company behind the product.
  • Capabilities we simply do not have. Open tracking, automatic resend of failed emails, email batching and quota scheduling, a backup connection. If your operation needs those, the licence buys them.

05 · The other side

Where Custom SMTP
is ahead.

The same standard applies in this direction: each point is verifiable, in the code or on the screen.

  • The paid mailers are free here. Amazon SES, Outlook and Zoho are behind their licence; here SES rides the API with an IAM role and no stored keys, and Outlook and Zoho are ordinary free presets over SMTP.
  • Alerts beyond the failure notice. Volume spikes with absolute thresholds, consecutive-failure and failure-rate rules, and a webhook channel, all free; their webhook and chat channels are Pro.
  • Configuration as code, completely. Every setting can be forced from a PHP constant or an environment variable, network-wide on multisite, for immutable and containerised WordPress. Their pages do not advertise an equivalent.
  • WordPress notification switches. Turning off the automatic emails WordPress sends on its own ships free here and is not advertised on their pages.
  • Nothing else in the box. No account, no third-party relay, no telemetry, no tracking pixels, no upsell banner in wp-admin. The full list is short and it is the point.
  • French, completely. The plugin and this documentation site exist fully in both English and French, screens included.

06 · The short version

How to
choose.

Two sentences each, no hedging.

Take Post SMTP if the mobile app or the Chrome extension would genuinely change how fast you learn about failures, if you want one-click OAuth setups and a guided wizard, or if you need open tracking, automatic resend or a backup connection and the licence cost is fine. Their free tier is a real tool, more open than WP Mail SMTP’s.

Take Custom SMTP if you want Amazon SES, Outlook and Zoho without a licence, alerts that also catch a compromised form, configuration that lives in code, and a plugin that sends nothing anywhere except your email, in English and in French. That is the whole offer, and it stays free.

Try the ten-minute version

Install, pick your provider from the preset list, send yourself a test. The twelve guides carry the exact values, provider by provider.

The provider guides

The other comparisons

Same method, same standard: against WP Mail SMTP and against FluentSMTP, every claim sourced on their own pages and dated.

All comparisons

Sources, all checked on 30 July 2026: the Post SMTP pricing page (licences from $59.99 to $99.99 a year, Pro mailers, one-click setups, alert channels, resend and batching features) and the Post SMTP listing on WordPress.org (installations, reviews, free features, wizard, DNS checks, mobile app and Chrome extension, tested-up-to). Facts about Custom SMTP are verifiable in its public code. Found something outdated? Say so on the support forum and this page gets fixed.