Post SMTP is WPExperts’ WordPress mailer plugin. It replaces WordPress’s default wp_mail() with authenticated SMTP or a provider API, the same job WP Mail SMTP and FluentSMTP do. The category-distinguishing feature is the failure-alerting layer: when a send fails, the free plugin can push the alert to its own mobile app, a Chrome extension, Slack, Pushover, a webhook, or the admin email address, and Pro adds Microsoft Teams and Twilio SMS. FluentSMTP also sends free alerts (Slack, Discord, Telegram, Pushover); what neither it nor WP Mail SMTP has is a first-party mobile app.
The plugin was first published to wp.org in October 2017 by Saad Iqbal and is now maintained by 
WPExperts. The wp.org listing reports 300,000+ active installs at a 4.7 rating across 525 reviews, current version 4.0.1 (released August 2026), tested up to WordPress 7.0.4. The free version is on the wordpress.org repository; a three-tier annual Pro subscription is sold separately at postmansmtp.com.
The short recommendation: Post SMTP is the right pick for an operator who wants push-to-phone alerts on failed mail without paying for WP Mail SMTP Pro to get them. Operators monitoring a site at 11pm get a push notification on a phone they were already going to look at, instead of an email in an inbox they were not. For sites that want per-from-address routing across multiple mailers, FluentSMTP remains the recommendation. For sites that want the largest free mailer catalogue and a paid support SLA, WP Mail SMTP remains the recommendation.
What the free version includes
Everything below ships in the wordpress.org plugin at no cost:
- 3-step setup wizard that auto-detects SMTP settings, accepts credentials or an OAuth flow, and runs a test send before saving.
- OAuth 2.0 for Gmail / Google Workspace in the free plugin, and for Microsoft 365 / Outlook in the paid Pro extension (One-Click setup through Post SMTP’s own app needs the Business plan). Less Secure App (LSA) access was Google's name for the third-party authentication path that used a plain account password against Gmail's SMTP, IMAP, and POP endpoints. Google shut it down for consumer accounts on 30 May 2022 and for Workspace accounts on 1 May 2025; OAuth, App Passwords, or a different sending provider replace it. Read full reference → are not required for either provider. Microsoft 365 OAuth is the one piece of category geography most worth knowing: Post SMTP and WP Mail SMTP both charge for it, and FluentSMTP is the free route. For Microsoft 365 shops the choice is often decided there. See the Google OAuth credentials walkthrough for the Gmail setup steps.
- Email logging with filterable search across recipient, subject, status, and timestamp. Failed sends can be resent from the log.
- Backup SMTP connection that takes over when the primary fails.
- Failure notifications to: the Post SMTP mobile app (iOS and Android push), the Chrome extension, Slack, Pushover, arbitrary webhooks, or the admin email address. Microsoft Teams (Business plan) and Twilio SMS alerts are Pro.
- SPF, DKIM, and DMARC diagnostic checks run from the settings screen to flag misconfigured DNS before mail starts bouncing.
Mail is sent in real time; there is no in-plugin Action Scheduler queue, so timeout-sized bursts have to be handled provider-side.
The WP mail config generator takes a provider API key or SMTP credential pair and returns a paste-ready block for Post SMTP’s mailer settings, so the setup wizard’s credential step becomes copy-paste. The DNS auth checker reads how the chosen provider’s SPF include and DKIM records resolve from the receiver’s perspective, adding a receiver-side view to Post SMTP’s in-plugin SPF/DKIM/DMARC diagnostics.
The mobile app, concretely
The Post SMTP mobile app is a separate iOS and Android download (free) that pairs to one or more WordPress sites running the plugin. Out of the box it surfaces a live email log, push notifications on failed sends, and error details. Two capabilities are Pro-gated on the app side: one-tap resend of a failed message, and connecting more than one site to a single device. Operators who want a phone notification when transactional mail breaks get it in the free tier; operators who want to act on it from the phone, or monitor an estate of client sites from one device, need the subscription.
Native mailer integrations
The free plugin ships native API integrations with the following providers, plus a generic SMTP option for anything else:
SendGrid, Mailgun, Postmark, Brevo, SparkPost, SMTP2GO, Elastic Email, Mailjet, Resend, Gmail / Google Workspace, SMTP.com, Mandrill, plus Mailtrap, Sweego, MailerSend, and Cloudflare Email Sending. Amazon SES, Zoho Mail, and Microsoft 365 / Outlook are Pro extensions.
Pro tiers
Pro is sold as three annual tiers plus a lifetime option, with a 14-day money-back guarantee. Verified against postmansmtp.com/pricing on 2026-08-11:
| Tier | Price | Adds on top of free |
|---|---|---|
| Basic | $59.99/year | All Pro mailer integrations, Gmail one-click setup, standard support |
| Professional | $79.99/year | Advanced delivery features, bulk email resend from the log, priority support |
| Business | $99.99/year | Microsoft one-click setup, MS Teams notifications, mobile app premium features, expert-assisted setup |
The tier matrix is less granular than WP Mail SMTP Pro’s published feature table; the marketing copy does not name which specific Pro mailers each tier unlocks. Operators returning to Post SMTP after a multi-year gap may remember the older per-extension product line (Office365 API, SES API, Twilio Pro extensions sold separately). That model is gone; the features are inside the three tiers above.
Where Post SMTP is weaker
Three limitations matter for a buying decision.
- No per-from-address routing. Post SMTP supports primary plus fallback; the Pro secondary connection covers auto-routing when a send fails, not steering by sender. FluentSMTP and WP Mail SMTP Pro both support routing rules that send different from-addresses through different mailers. Sites that send transactional mail from
noreply@and marketing mail fromnews@and want them on separate providers will find Post SMTP’s connection model too narrow. - No background queue. High-volume sends share the request lifecycle with the page that triggered them; large bursts can hit PHP timeout limits. Pro adds “Email Batching and Quota Scheduling,” but that is rate-limiting, not asynchronous queueing.
- Smaller installed base than the leaders. 300,000+ active installs is substantial, but WP Mail SMTP reports 4 million and FluentSMTP reports 600,000. For agencies betting on a single plugin across many client sites, the larger installed base is a hedge.
Assessment
Post SMTP is nanoPost’s recommendation for WordPress sites that want phone-push alerts on transactional-email failure and do not want to subscribe to WP Mail SMTP Pro to get them. The mobile-app channel is genuine product differentiation: it is the only mailer plugin in the leading three that ships a first-party mobile alert path, and it ships in the free plugin. Microsoft 365 OAuth is not part of that case: it is a Pro feature here, as it is at WP Mail SMTP.
FluentSMTP is the better default for sites that want logging, fallback, and per-from-address routing without paying for any of them and do not need the mobile-alert layer. WP Mail SMTP remains the right choice for sites that want the widest free mailer catalogue, the most polished setup wizard, or a paid support contract.
For operators who need the alert about broken email to reach a phone, not an inbox, Post SMTP is the plugin.
For the broader setup the plugin slots into, see how to set up WordPress email.
Plugin data verified September 2026 against 
wordpress.org/plugins/post-smtp and postmansmtp.com. Tested against version 4.0.1. Pricing tiers unchanged since the August review; SMTP.com and Cloudflare Email Sending were added as native mailers in 3.10.0 (August 2026).
Corrections
- 2026-10-19: an earlier version said the free plugin includes Microsoft 365 / Outlook OAuth and native Amazon SES and Zoho Mail integrations; Post SMTP 4.0.2 puts all three in its paid Pro extension (the free plugin’s Microsoft OAuth covers only
live.comhosts). - 2026-10-19: an earlier version listed Microsoft Teams and Twilio SMS among the free plugin’s failure-alert channels; both are Pro in Post SMTP 4.0.2 (Teams on the Business plan), and the free channels are the mobile app, Chrome extension, Slack, Pushover, webhook, and admin email.