WordPress sends email with PHP’s mail() function by default. Most hosts either block it or send it in a way that lands in spam, which is why contact form notifications, password resets and order confirmations go missing.

Dualsend SMTP Failover routes your site’s email through a mail server you control. What makes it different from other SMTP plugins is the second server: configure a fallback, and if the primary one is down, rate limited or refusing connections, the message is retried on the backup automatically. Nothing is lost while you work out what went wrong with the first one.

How delivery works

Each message is offered to the configured routes in order, and the first one that accepts it wins:

Primary provider API, if the primary server is set to API mode
Primary SMTP server
Fallback provider API, if the fallback server is set to API mode
Fallback SMTP server

If every route fails, the message is handed back to WordPress so its own mail handling still gets a turn.

Sending over an API instead of SMTP

Many hosts close outgoing SMTP ports. Where a provider offers an HTTP API, you can use it instead of SMTP by pasting in an API key — no ports involved. These providers are supported:

Brevo, Elastic Email, MailerSend, Mailgun, Mailjet, Mandrill, Postmark, Resend, SendGrid, SendLayer, SMTP.com, SMTP2GO, SparkPost.

Any other provider, including Amazon SES, Gmail, Google Workspace, Microsoft 365, Outlook.com and Zoho Mail, works over standard SMTP.

Features

Two independent servers, with automatic failover between them
SMTP or provider API for each server, mixed freely
Connection and credential tests built into the settings screen
A test message that follows the same routes as your real email
Optional debug log, with passwords and API keys masked before anything is written
Short timeouts while a visitor is waiting on a form submission, so a slow mail server never holds up the page
Works with Contact Form 7 and any other plugin that sends through wp_mail()

External services

This plugin does not contact any service on its own. It has no telemetry, no licence check, and no connection to any service run by the plugin author.

The only outgoing connections it makes are to the email provider you configure, and only when it is sending your mail or when you press one of the test buttons. Endpoints below are API hostnames, not web pages.

Brevo — sends to api.brevo.com — terms, privacy
Elastic Email — sends to api.elasticemail.com — terms, privacy
MailerSend — sends to api.mailersend.com — terms, privacy
Mailgun — sends to api.mailgun.net or api.eu.mailgun.net — terms, privacy
Mailjet — sends to api.mailjet.com — terms, privacy
Mandrill — sends to mandrillapp.com — terms, privacy
Postmark — sends to api.postmarkapp.com — terms, privacy
Resend — sends to api.resend.com — terms, privacy
SendGrid — sends to api.sendgrid.com — terms, privacy
SendLayer — sends to console.sendlayer.com — terms, privacy
SMTP.com — sends to api.smtp.com — terms, privacy
SMTP2GO — sends to api.smtp2go.com — terms, privacy
SparkPost — sends to api.sparkpost.com or api.eu.sparkpost.com — terms, privacy

When a message is sent, the data passed to your chosen provider is the message itself: recipients, subject, body, and the sender address you configured. That is the same data any mail server would receive. Nothing is sent anywhere else.

If you configure a plain SMTP server instead of an API, the plugin connects only to the host you entered.