How to use Mailpit with PHP.

Mailpit is a small, open-source mail catcher: an SMTP server that accepts everything and delivers nothing, plus a web interface to read what arrived. It's a single Go binary and is widely used as the maintained successor to MailHog.

• SMTP on port 1025 accepts mail from your app, with no authentication by default.
• Web UI on port 8025 shows each message's HTML, plain text, headers, raw source and attachments, with search.
• It has tools for checking HTML compatibility across mail clients and finding broken links, plus a REST API that automated tests can query.

The point is safety as much as convenience. A local copy of a production database is full of real customer addresses. Without a catcher, one test checkout can email a real person.

wp_mail() uses PHPMailer, which by default calls PHP's mail(). If you've set sendmail_path as above, WordPress mail already goes to Mailpit and there's nothing else to do.

To use SMTP instead, for example because production uses an SMTP plugin and you want the same code path, drop a must-use plugin into wp-content/mu-plugins/mailpit.php:

<?php
add_action( 'phpmailer_init', function ( $phpmailer ) {
    $phpmailer->isSMTP();
    $phpmailer->Host        = '127.0.0.1';
    $phpmailer->Port        = 1025;
    $phpmailer->SMTPAuth    = false;
    $phpmailer->SMTPAutoTLS = false;
} );

A quick test with WP-CLI: wp eval 'wp_mail("test@example.com", "Test", "Hello");'. If an SMTP plugin from production is active locally, it may override this hook with real credentials. Deactivate it on your local copy.

• mail() returns true but nothing arrives. The web server's PHP is still using the old sendmail_path. Compare the value in phpinfo() with the CLI, and restart php-fpm. A true return only means the message was handed to the sendmail command.
• Connection refused on port 1025. Mailpit isn't running (brew services list), or something else is on that port (lsof -i :1025).
• TLS or STARTTLS errors. The client is trying to encrypt a connection Mailpit doesn't offer. Set encryption to none. In PHPMailer that's SMTPAutoTLS = false, and in a Laravel .env leave the encryption setting empty.
• Messages disappear after a restart. By default Mailpit keeps its messages in a temporary database. Start it with --database /path/to/mailpit.db if you want them kept.
• A real email went out. The app sent through an API-based mailer (Mailgun, Postmark, SES) instead of SMTP or mail(). Switch the local mailer to SMTP, or use the provider's sandbox mode.

Bothy ships Mailpit as an add-on. Enable it once and PHP's mail() is wired to it automatically for every site. There's no sendmail_path to edit. The inbox is at https://mail.test, and unread messages show as a badge on Mail in the sidebar. Frameworks that use SMTP get the same settings as above: host 127.0.0.1, port 1025, no auth.

bothy mail --enable             # install and start Mailpit
bothy mail                      # open https://mail.test
bothy mail --list               # recent messages
bothy mail --clear              # empty the inbox

The Laravel, Symfony and WordPress starters create a site with its database config already written. For Laravel and Symfony, set the mail variables as above, which you can do from the site's Environment tab or with bothy site env. Mailpit is also reachable through the MCP server, so an AI agent can trigger a password reset and then read the email it produced.