WordPress sends email with PHP’s mail() function by default, which many hosts block or send to spam. Dualsend SMTP Failover routes your email through a mail server you choose, over SMTP or a provider API, and switches to a second server when the first one fails.
How delivery works
- The Primary SMTP Server (API first when set to API mode, then SMTP).
- The Fallback SMTP Server, while its switch is on, in the same way, with no waiting in the page.
- Background retries, when both servers fail: the email waits in a queue and is tried again every Retry Interval minutes, up to Maximum Retries times.
- WordPress itself, as a last resort after the last retry, or at once when Maximum Retries is 0.
Features
- Primary and fallback mail servers, each over SMTP or a provider API, with automatic failover
- Connection and credential tests on the settings screen
- A test message that follows the same route as your real email
- Optional debug log, with passwords and API keys masked and no message bodies
- Works with Contact Form 7, WooCommerce and any plugin that sends through
wp_mail()
API providers: Brevo, Elastic Email, MailerSend, Mailgun, Mailjet, Mandrill, Postmark, Resend, SendGrid, SendLayer, SMTP.com, SMTP2GO, SparkPost. Any other provider, such as Amazon SES, Gmail, Microsoft 365 or Zoho Mail, works over SMTP.
Fonts: Inter and Plus Jakarta Sans, bundled under the SIL Open Font License 1.1.
External services
The plugin connects to the email provider you configure, when it sends your mail or when you press a test button. It sends that provider the message itself: recipients, subject, body and your sender address. With plain SMTP it connects only to the host you entered.
Install reports, only if you allow them. The settings page asks, as do the Dashboard and the Plugins screen until answered or you click Not now. Nothing is sent until an administrator clicks Allow. Then the site sends wpsmtpfallback.com, run by the plugin author, a report at once, weekly, and on deactivation or deletion: a random ID and signing key, the site name, address and admin email, the WordPress, PHP and plugin versions, whether it is a network, and the mail setup (SMTP or API and the provider of each server, fallback on or off). Never a server name, username, password, API key or message content. The country comes from the request IP address, which our install records do not keep but our server logs do. Deactivating pauses the reports. Stop sharing on the settings page, or deleting the plugin, ends them and removes the site name and admin email from our install records, not from emails already sent to us. terms, privacy
- Brevo: api.brevo.com. terms, privacy
- Elastic Email: api.elasticemail.com. terms, privacy
- MailerSend: api.mailersend.com. terms, privacy
- Mailgun: api.mailgun.net or api.eu.mailgun.net. terms, privacy
- Mailjet: api.mailjet.com. terms, privacy
- Mandrill: mandrillapp.com. terms, privacy
- Postmark: api.postmarkapp.com. terms, privacy
- Resend: api.resend.com. terms, privacy
- SendGrid: api.sendgrid.com. terms, privacy
- SendLayer: console.sendlayer.com. terms, privacy
- SMTP.com: api.smtp.com. terms, privacy
- SMTP2GO: api.smtp2go.com. terms, privacy
- SparkPost: api.sparkpost.com or api.eu.sparkpost.com. terms, privacy
Feedback tab. Nothing is sent until an administrator fills in the form, ticks the consent box and presses Send feedback. The message then goes through your own mail server to the Dualsend team at cshubham832@gmail.com and iamshubhamchaurasia@gmail.com. It contains the rating, the message, the optional name and email, your site address and the plugin version.
Screenshots
The Settings tab: the sender identity and both SMTP servers, each with a passed connection test.
The primary server set to API delivery, with a provider chosen and its API key verified.
The Delivery and Diagnostics card and the Save Settings bar.
The Test tab after a test message.
The Logs tab: the fallback server delivered a message after the primary server failed.
The Feedback tab, which sends a rating and a message only on submit.