Comparison

Custom SMTP vs WP Mail SMTP.

Both plugins fix the same problem the same way: they route WordPress email through an authenticated provider. The difference is the model. Every claim about WP Mail SMTP below comes from their own listing, pricing page 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 an SMTP provider you configure, which is the actual fix for WordPress email.
  • Both are free to install from WordPress.org, GPL-licensed, with no account required to send.
  • Both are actively maintained and tested against current WordPress.
  • Both let you lock settings in code with PHP constants, so a client cannot break a working configuration from wp-admin.

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.

WP Mail SMTP is the free tier of a commercial product. The features that tell you whether your email actually works, the email log, the failure alerts, the resend button, and the Amazon SES, Microsoft 365 and Zoho mailers, are in the paid version, from $49 to $399 a year depending on the licence. That is a legitimate business, run well, at very large scale.

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, and no add-on catalogue.

03 · Side by side

Feature by feature,
sourced and dated.

“Pro” means WP Mail SMTP’s paid licence, from $49 a year. Sources for every row are at the bottom of the page.

Comparison · 30 July 2026 free means free
WP Mail SMTPCustom SMTP
Send through your SMTP providerFree, 12 mailersFree, 12 presets + any SMTP server
Amazon SESProFree, API with IAM role, no stored keys
Outlook / Microsoft 365Pro, via the Microsoft APIFree preset, via SMTP
Zoho MailProFree preset
Email log, preview, resend, CSV exportProFree
Failure & volume alertsPro · email, Slack, Teams, Discord, SMS, webhookFree · email, webhook, admin notice
WordPress notification switchesPro, “Email Controls”Free
Open & click trackingProNot offered, by design
Backup connection, routing, rate limitingProNot offered
Setup wizard, migration from other pluginsFreeNo wizard: presets fill the settings
Settings locked in codePHP constantsPHP constants and environment variables, every setting
PriceFree, then $49 to $399 / yearFree, no paid version

One nuance worth knowing on Outlook: 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 and what it means for a small site.

04 · Credit where due

What WP Mail SMTP
does better.

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

  • Scale and track record. Four million active installations and more than five thousand reviews at 4.8 stars. That weight of usage catches regressions early and buys years of edge cases fixed.
  • More built-in API mailers. SendLayer, SMTP.com, SparkPost, Elastic Email, SMTP2GO and others ship in their free version; Gmail and Microsoft sending goes through OAuth APIs rather than app passwords.
  • The onboarding. A guided setup wizard, one-click migration of settings from other SMTP plugins, and on the Elite licence a team that does the DNS work for you.
  • Capabilities we simply do not have. Open and click tracking, backup connections with smart routing, rate limiting, delivery reports. If your operation needs those, there is no free equivalent here.
  • A documentation network. Hundreds of pages covering every mailer and every error message, in eight languages, continuously updated.

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 diagnostic features are free. The email log with preview, resend and CSV export, the failure and volume alerts, and the notification switches: everything this site documents is in the one free version. In WP Mail SMTP, that list is the paid tier.
  • Amazon SES without stored secrets. Sending through the SES API authenticated by the server’s IAM role, with no access keys in the database, is a free Custom SMTP feature with no equivalent in their offer at any price.
  • Configuration as code, completely. Every setting, not a subset, can be forced from a PHP constant or an environment variable, including on FrankenPHP and Bedrock-style stacks. Built for immutable and containerised WordPress.
  • Nothing else in the box. No account, no third-party relay in the path, no telemetry, no tracking pixels, no banner in wp-admin, no data leaving your site. The full list is short and it is the point.
  • French, completely. The plugin and this documentation exist fully in both English and French, screens included.

06 · The short version

How to
choose.

Two sentences each, no hedging.

Take WP Mail SMTP if you want open and click tracking, backup connections and routing, a proprietary API mailer like SendLayer or SparkPost, or a vendor with a support contract behind it, and the licence cost is fine. The free version will route your mail, but the features that answer “did it arrive?” are paid.

Take Custom SMTP if you want the sending, the log, the alerts and the switches complete and free, Amazon SES without stored keys, configuration that lives in code, and a plugin that sends nothing anywhere except your email. 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 FluentSMTP and against Post SMTP, every claim sourced on their own pages and dated.

All comparisons

Sources, all checked on 30 July 2026: the WP Mail SMTP listing on WordPress.org (installations, reviews, free mailers, Pro feature list), their pricing page (licences from $49 to $399 a year, feature gating), their constants documentation and their Email Controls documentation (“You will need the WP Mail SMTP Pro license to unlock the Email Controls option”). Facts about Custom SMTP are verifiable in its public code. Found something outdated? Say so on the support forum and this page gets fixed.